<Page>

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM N-CSR

                   CERTIFIED SHAREHOLDER REPORT OF REGISTERED
                         MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number: 811-21024

             Active Assets Institutional Government Securities Trust
               (Exact name of registrant as specified in charter)

            1221 Avenue of the Americas, New York, New York 10020
           (Address of principal executive offices)      (Zip code)

                                Ronald E. Robison
              1221 Avenue of the Americas, New York, New York 10020
                     (Name and address of agent for service)

Registrant's telephone number, including area code: 212-762-4000

Date of fiscal year end: June 30, 2006

Date of reporting period: June 30, 2006

Item 1 - Report to Shareholders
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Welcome, Shareholder:

In this report, you'll learn about how your investment in Active Assets
Institutional Government Securities Trust performed during the annual period. We
will provide an overview of the market conditions, and discuss some of the
factors that affected performance during the reporting period. In addition, this
report includes the Fund's financial statements and a list of Fund investments.

THIS MATERIAL MUST BE PRECEDED OR ACCOMPANIED BY A PROSPECTUS FOR THE FUND BEING
OFFERED.

MARKET FORECASTS PROVIDED IN THIS REPORT MAY NOT NECESSARILY COME TO PASS. THERE
IS NO ASSURANCE THAT A MUTUAL FUND WILL ACHIEVE ITS INVESTMENT OBJECTIVE. AN
INVESTMENT IN A MONEY MARKET FUND IS NOT INSURED OR GUARANTEED BY THE FEDERAL
DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY. ALTHOUGH THE FUND
SEEKS TO PRESERVE THE VALUE OF AN INVESTMENT AT $1.00 PER SHARE, IT IS POSSIBLE
TO LOSE MONEY BY INVESTING IN THE FUND. PLEASE SEE THE PROSPECTUS FOR MORE
COMPLETE INFORMATION ON INVESTMENT RISKS.

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FUND REPORT
FOR THE YEAR ENDED JUNE 30, 2006

MARKET CONDITIONS

During the 12-month period ended June 30, 2006, the Federal Open Market
Committee (the "Fed") continued the pattern of raising short-term rates it began
in June of 2004. Through 17 steps of 25 basis points each, including eight
during the 12 months covered by this report, the Fed increased its target rate
for federal funds from 1.00 percent to 5.25 percent, a five-year high.

Short-term rates rose alongside the federal funds rate, providing increased
return opportunities for investors in money market funds.

PERFORMANCE ANALYSIS

As of June 30, 2006, Active Assets Institutional Government Securities Trust had
net assets of approximately $668 million and an average portfolio maturity of 35
days. For the 12-month period ended June 30, 2006, the Fund provided a total
return of 4.15 percent. For the seven-day period ended June 30, 2006, the Fund
provided an effective annualized yield of 5.03 percent and a current yield of
4.91 percent, while its 30-day moving average yield for June was 4.86 percent.
PAST PERFORMANCE IS NO GUARANTEE OF FUTURE RESULTS.

Throughout the course of the Fund's fiscal year, we kept the portfolio's
weighted average maturity (a measure of interest rate sensitivity) short as
interest rates continued to rise. At the same time, we targeted maturities
around upcoming Fed meetings in order to capitalize on possible further interest
rate increases. Our strategy in managing the portfolio remained consistent with
the Fund's long-term focus on preservation of capital and liquidity. In keeping
with this approach, we emphasized high-quality government securities, and
avoided the use of derivatives or structured notes that might fluctuate
excessively with changing interest rates.

THERE IS NO GUARANTEE THAT ANY SECTORS MENTIONED WILL CONTINUE TO PERFORM AS
DISCUSSED HEREIN OR THAT SECURITIES IN SUCH SECTORS WILL BE HELD BY THE FUND IN
THE FUTURE.

PORTFOLIO COMPOSITION

U.S. Government Agencies -- Discount Notes        67.8%
U.S. Government Agencies -- Floating Rate Notes   26.9
Repurchase Agreement                               4.9
U.S. Government Agency -- Debenture Bond           0.4

MATURITY SCHEDULE

  1 - 30 Days    58.1%
 31 - 60 Days    16.7
 61 - 90 Days    18.6
 91 - 120 Days    1.5
121 + Days        5.1

DATA AS OF JUNE 30, 2006. SUBJECT TO CHANGE DAILY. ALL PERCENTAGES FOR PORTFOLIO
COMPOSITION AND MATURITY SCHEDULE ARE AS A PERCENTAGE OF TOTAL INVESTMENTS.
THESE DATA ARE PROVIDED FOR INFORMATIONAL PURPOSES ONLY AND SHOULD NOT BE DEEMED
A RECOMMENDATION TO BUY OR SELL THE SECURITIES MENTIONED. MORGAN STANLEY IS A
FULL-SERVICE SECURITIES FIRM ENGAGED IN SECURITIES TRADING AND BROKERAGE
ACTIVITIES, INVESTMENT BANKING, RESEARCH AND ANALYSIS, FINANCING AND FINANCIAL
ADVISORY SERVICES.


                                       2

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INVESTMENT STRATEGY

THE FUND INVESTS AT LEAST 80 PERCENT OF ITS ASSETS IN HIGH QUALITY, SHORT-TERM
U.S. GOVERNMENT SECURITIES. IN SELECTING INVESTMENTS, THE FUND'S "INVESTMENT
ADVISER," MORGAN STANLEY INVESTMENT ADVISORS INC., SEEKS TO MAINTAIN THE FUND'S
SHARE PRICE AT $1.00. THE SHARE PRICE REMAINING STABLE AT $1.00 MEANS THAT THE
FUND WOULD PRESERVE THE PRINCIPAL VALUE OF YOUR INVESTMENT.

AN INVESTMENT IN THE FUND IS NOT INSURED OR GUARANTEED BY THE FEDERAL DEPOSIT
INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY. ALTHOUGH THE FUND SEEKS TO
PRESERVE THE VALUE OF YOUR INVESTMENT AT $1.00 PER SHARE, IT IS POSSIBLE TO LOSE
MONEY BY INVESTING IN THE FUND.

FOR MORE INFORMATION ABOUT PORTFOLIO HOLDINGS

EACH MORGAN STANLEY FUND PROVIDES A COMPLETE SCHEDULE OF PORTFOLIO HOLDINGS IN
ITS SEMIANNUAL AND ANNUAL REPORTS WITHIN 60 DAYS OF THE END OF THE FUND'S SECOND
AND FOURTH FISCAL QUARTERS. THE SEMIANNUAL REPORTS AND THE ANNUAL REPORTS ARE
FILED ELECTRONICALLY WITH THE SECURITIES AND EXCHANGE COMMISSION (SEC) ON FORM
N-CSRS AND FORM N-CSR, RESPECTIVELY. MORGAN STANLEY ALSO DELIVERS THE SEMIANNUAL
AND ANNUAL REPORTS TO FUND SHAREHOLDERS AND MAKES THESE REPORTS AVAILABLE ON ITS
PUBLIC WEB SITE, www.morganstanley.com. EACH MORGAN STANLEY FUND ALSO FILES A
COMPLETE SCHEDULE OF PORTFOLIO HOLDINGS WITH THE SEC FOR THE FUND'S FIRST AND
THIRD FISCAL QUARTERS ON FORM N-Q. MORGAN STANLEY DOES NOT DELIVER THE REPORTS
FOR THE FIRST AND THIRD FISCAL QUARTERS TO SHAREHOLDERS, NOR ARE THE REPORTS
POSTED TO THE MORGAN STANLEY PUBLIC WEB SITE. YOU MAY, HOWEVER, OBTAIN THE FORM
N-Q FILINGS (AS WELL AS THE FORM N-CSR AND N-CSRS FILINGS) BY ACCESSING THE
SEC'S WEB SITE, http://www.sec.gov. YOU MAY ALSO REVIEW AND COPY THEM AT THE
SEC'S PUBLIC REFERENCE ROOM IN WASHINGTON, DC. INFORMATION ON THE OPERATION OF
THE SEC'S PUBLIC REFERENCE ROOM MAY BE OBTAINED BY CALLING THE SEC AT (800)
SEC-0330. YOU CAN ALSO REQUEST COPIES OF THESE MATERIALS, UPON PAYMENT OF A
DUPLICATING FEE, BY ELECTRONIC REQUEST AT THE SEC'S E-MAIL ADDRESS
(publicinfo@sec.gov) OR BY WRITING THE PUBLIC REFERENCE SECTION OF THE SEC,
WASHINGTON, DC 20549-0102.

HOUSEHOLDING NOTICE

TO REDUCE PRINTING AND MAILING COSTS, THE FUND ATTEMPTS TO ELIMINATE DUPLICATE
MAILINGS TO THE SAME ADDRESS. THE FUND DELIVERS A SINGLE COPY OF CERTAIN
SHAREHOLDER DOCUMENTS, INCLUDING SHAREHOLDER REPORTS, PROSPECTUSES AND PROXY
MATERIALS, TO INVESTORS WITH THE SAME LAST NAME WHO RESIDE AT THE SAME ADDRESS.
YOUR PARTICIPATION IN THIS PROGRAM WILL CONTINUE FOR AN UNLIMITED PERIOD OF TIME
UNLESS YOU INSTRUCT US OTHERWISE. YOU CAN REQUEST MULTIPLE COPIES OF THESE
DOCUMENTS BY CALLING (800) 350-6414, 8:00 A.M. TO 8:00 P.M., ET. ONCE OUR
CUSTOMER SERVICE CENTER HAS RECEIVED YOUR INSTRUCTIONS, WE WILL BEGIN SENDING
INDIVIDUAL COPIES FOR EACH ACCOUNT WITHIN 30 DAYS.


                                       3

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EXPENSE EXAMPLE

As a shareholder of the Fund, you incur ongoing costs, including advisory fees
and other Fund expenses. This example is intended to help you understand your
ongoing costs (in dollars) of investing in the Fund and to compare these costs
with the ongoing costs of investing in other mutual funds.

The example is based on an investment of $1,000 invested at the beginning of the
period and held for the entire period 01/01/06 - 06/30/06.

ACTUAL EXPENSES

The first line of the table below provides information about actual account
values and actual expenses. You may use the information in this line, together
with the amount you invested, to estimate the expenses that you paid over the
period. Simply divide your account value by $1,000 (for example, an $8,600
account value divided by $1,000 = 8.6), then multiply the result by the number
in the first line under the heading entitled "Expenses Paid During Period" to
estimate the expenses you paid on your account during this period.

HYPOTHETICAL EXAMPLE FOR COMPARISON PURPOSES

The second line of the table below provides information about hypothetical
expenses based on the Fund's actual expense ratio and an assumed rate of return
of 5% per year before expenses, which is not the Fund's actual return. The
hypothetical account values and expenses may not be used to estimate the actual
ending account balance or expenses you paid for the period. You may use this
information to compare the ongoing cost of investing in the Fund and other
funds. To do so, compare this 5% hypothetical example with the 5% hypothetical
examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your
ongoing costs only. Therefore, the second line of the table is useful in
comparing ongoing costs, and will not help you determine the relative total cost
of owning different funds that have transactional costs, such as sales charges
(loads), and redemption fees, or exchange fees.

<Table>
<Caption>
                                                    BEGINNING         ENDING       EXPENSES PAID
                                                  ACCOUNT VALUE   ACCOUNT VALUE   DURING PERIOD *
                                                  -------------   -------------   ---------------
                                                                                    01/01/06 -
                                                     01/01/06        06/30/06         06/30/06
                                                  -------------   -------------   ---------------
                                                                              
Actual (2.27% return)                               $1,000.00       $1,022.70          $0.75
Hypothetical (5% annual return before expenses)     $1,000.00       $1,023.92          $0.75
</Table>

- ----------
*    EXPENSES ARE EQUAL TO THE FUND'S ANNUALIZED EXPENSE RATIO OF 0.15%
     MULTIPLIED BY THE AVERAGE ACCOUNT VALUE OVER THE PERIOD, MULTIPLIED BY
     181/367** (TO REFLECT THE ONE-HALF YEAR PERIOD). IF THE FUND HAD BORNE ALL
     OF ITS EXPENSES, THE ANNUALIZED EXPENSE RATIO WOULD HAVE BEEN 0.20%.

**   ADJUSTED TO REFLECT NON-BUSINESS DAY ACCRUALS.


                                       4

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INVESTMENT ADVISORY AGREEMENT APPROVAL

NATURE, EXTENT AND QUALITY OF SERVICES

The Board reviewed and considered the nature and extent of the investment
advisory services provided by the Investment Adviser under the Advisory
Agreement, including portfolio management, investment research and fixed income
securities trading. The Board also reviewed and considered the nature and extent
of the non-advisory, administrative services provided by the Fund's
Administrator under the Administration Agreement, including accounting,
clerical, bookkeeping, compliance, business management and planning, and the
provision of supplies, office space and utilities at the Investment Adviser's
expense. (The Investment Adviser and the Administrator together are referred to
as the "Adviser" and the Advisory and Administration Agreements together are
referred to as the "Management Agreement.") The Board also compared the nature
of the services provided by the Adviser with similar services provided by
non-affiliated advisers as reported to the Board by Lipper Inc. ("Lipper").

The Board reviewed and considered the qualifications of the portfolio managers,
the senior administrative managers and other key personnel of the Adviser who
provide the advisory and administrative services to the Fund. The Board
determined that the Adviser's portfolio managers and key personnel are well
qualified by education and/or training and experience to perform the services in
an efficient and professional manner. The Board concluded that the nature and
extent of the advisory and administrative services provided were necessary and
appropriate for the conduct of the business and investment activities of the
Fund. The Board also concluded that the overall quality of the advisory and
administrative services was satisfactory.

PERFORMANCE RELATIVE TO COMPARABLE FUNDS MANAGED BY OTHER ADVISERS

On a regular basis, the Board reviews the performance of all funds in the Morgan
Stanley Fund Complex, including the Fund, compared to their peers, paying
specific attention to the underperforming funds. In addition, the Board
specifically reviewed the Fund's performance for the one-, three- and five-year
periods ended November 30, 2005, as shown in a report provided by Lipper (the
"Lipper Report"), compared to the performance of comparable funds selected by
Lipper (the "performance peer group"). The Board also discussed with the Adviser
the performance goals and the actual results achieved in managing the Fund. The
Board concluded that the Fund's performance was competitive with that of its
performance peer group.

FEES RELATIVE TO OTHER PROPRIETARY FUNDS MANAGED BY THE ADVISER WITH COMPARABLE
INVESTMENT STRATEGIES

The Board noted that the Adviser did not manage any other proprietary funds with
investment strategies comparable to those of the Fund.

FEES AND EXPENSES RELATIVE TO COMPARABLE FUNDS MANAGED BY OTHER ADVISERS

The Board reviewed the advisory and administrative fee (together, the
"management fee") rate and total expense ratio of the Fund as compared to the
average management fee rate and average total expense ratio for funds,


                                        5

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selected by Lipper (the "expense peer group"), managed by other advisers with
investment strategies comparable to those of the Fund, as shown in the Lipper
Report. The Board concluded that the Fund's management fee rate and total
expense ratio were competitive with those of its expense peer group.

BREAKPOINTS AND ECONOMIES OF SCALE

The Board reviewed the structure of the Fund's management fee schedule under the
Management Agreement and noted that it does not include any breakpoints. The
Board also reviewed the level of the Fund's management fee and concluded that
the fee, compared to the Fund's expense peer group, was sufficiently low, so
that, in effect, economics of scale were built into the management fee
structure.

PROFITABILITY OF THE ADVISER AND AFFILIATES

The Board considered information concerning the costs incurred and profits
realized by the Adviser and affiliates during the last year from their
relationship with the Fund and during the last two years from their relationship
with the Morgan Stanley Fund Complex and reviewed with the Adviser the cost
allocation methodology used to determine the profitability of the Adviser and
affiliates. Based on its review of the information it received, the Board
concluded that the profits earned by the Adviser and affiliates were not
excessive in light of the advisory, administrative and other services provided
to the Fund.

FALL-OUT BENEFITS

The Board considered so-called "fall-out benefits" derived by the Adviser and
affiliates from their relationship with the Fund and the Morgan Stanley Fund
Complex, such as "float" benefits derived from handling of checks for purchases
and sales of Fund shares, through a broker-dealer affiliate of the Adviser. The
Board concluded that the float benefits were relatively small.

SOFT DOLLAR BENEFITS

The Board considered whether the Adviser realizes any benefits from commissions
paid to brokers who execute securities transactions for the Fund ("soft
dollars"). The Board noted that the Fund invests only in fixed income
securities, which do not generate soft dollars.

ADVISER FINANCIALLY SOUND AND FINANCIALLY CAPABLE OF MEETING THE FUND'S NEEDS

The Board considered whether the Adviser is financially sound and has the
resources necessary to perform its obligations under the Management Agreement.
The Board noted that the Adviser's operations remain profitable, although
increased expenses in recent years have reduced the Adviser's profitability. The
Board concluded that the Adviser has the financial resources necessary to
fulfill its obligations under the Management Agreement.


                                        6

<Page>

HISTORICAL RELATIONSHIP BETWEEN THE FUND AND THE ADVISER

The Board also reviewed and considered the historical relationship between the
Fund and the Adviser, including the organizational structure of the Adviser, the
policies and procedures formulated and adopted by the Adviser for managing the
Fund's operations and the Board's confidence in the competence and integrity of
the senior managers and key personnel of the Adviser. The Board concluded that
it is beneficial for the Fund to continue its relationship with the Adviser.

OTHER FACTORS AND CURRENT TRENDS

The Board considered the controls and procedures adopted and implemented by the
Adviser and monitored by the Fund's Chief Compliance Officer and concluded that
the conduct of business by the Adviser indicates a good faith effort on its part
to adhere to high ethical standards in the conduct of the Fund's business.

GENERAL CONCLUSION

After considering and weighing all of the above factors, the Board concluded
that it would be in the best interest of the Fund and its shareholders to
approve renewal of the Management Agreement for another year.


                                        7

<Page>

ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST
PORTFOLIO OF INVESTMENTS - JUNE 30, 2006

<Table>
<Caption>
                                                                 ANNUALIZED
PRINCIPAL                                                         YIELD ON
AMOUNT IN                                                          DATE OF           MATURITY
THOUSANDS                    DESCRIPTION                          PURCHASE            DATES              VALUE
- -----------------------------------------------------------------------------------------------------------------
                                                                                         
            U.S. Government Agencies - Discount Notes (67.8%)
  $20,000   Federal Farm Credit Banks                                   5.02%        07/03/06        $ 20,000,000
  339,209   Federal Home Loan Banks                              4.58 - 5.18   07/03/06 - 11/22/06    338,223,659
   39,490   Federal National Mortgage Assoc.                     4.57 - 5.14   07/12/06 - 11/01/06     39,186,270
   55,981   Freddie Mac                                          4.58 - 5.14   07/11/06 - 11/28/06     55,474,844
                                                                                                     ------------
            Total U.S. Government Agencies - Discount Notes
               (COST $452,884,773)                                                                    452,884,773
                                                                                                     ------------
            U.S. Government Agencies - Floating Rate
               Notes (26.9%)
   69,075   Federal Farm Credit Banks                            5.00 - 5.32+  07/01/06 - 09/22/06*    69,069,013
   80,625   Federal Home Loan Banks                              4.86 - 5.19+  07/04/06 - 09/13/06*    80,614,935
   30,000   Freddie Mac                                          4.87 - 5.30+  07/06/06 - 09/22/06*    29,989,517
                                                                                                     ------------
            Total U.S. Government Agencies - Floating
               Rate Notes
               (COST $179,673,465)                                                                    179,673,465
                                                                                                     ------------
            Repurchase Agreement (4.9%)
   32,615   Banc of America Securities, LLC (dated 06/30/06;
            proceeds  $32,629,405) (a) (COST $32,615,000)               5.30         07/03/06          32,615,000
                                                                                                     ------------
            U.S. Government Agency - Debenture Bond (0.3%)
    2,500   Federal Home Loan Banks
               (COST $2,464,050)                                        5.18         05/15/07           2,464,050
                                                                                                     ------------
            Total Investments
               (COST $667,637,288) (b)                                                   99.9%        667,637,288
            Other Assets in Excess of Liabilities                                         0.1             526,268
                                                                                        -----        ------------
            Net Assets                                                                  100.0%       $668,163,556
                                                                                        =====        ============
</Table>

- ----------
+    RATES SHOWN ARE THE RATES IN EFFECT AT JUNE 30, 2006.

*    DATES OF NEXT INTEREST RATES RESET.

(a)  COLLATERALIZED BY FEDERAL NATIONAL MORTGAGE ASSOC. 5.50% DUE 09/01/35 -
     12/01/35 VALUED AT $33,267,300.

(b)  COST IS THE SAME FOR FEDERAL INCOME TAX PURPOSES.

                        SEE NOTES TO FINANCIAL STATEMENTS


                                        8

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ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST
FINANCIAL STATEMENTS

Statement of Assets and Liabilities
JUNE 30, 2006

Assets:
Investments in securities, at value (cost $667,637,288)             $667,637,288
Cash                                                                       3,042
Interest receivable                                                      871,341
Prepaid expenses and other assets                                         63,536
                                                                    ------------
   Total Assets                                                      668,575,207
                                                                    ------------
Liabilities:
Payable for:
   Dividends to shareholders                                             271,058
   Administration fee                                                     28,552
   Investment advisory fee                                                23,600
Accrued expenses and other payables                                       88,441
                                                                    ------------
   Total Liabilities                                                     411,651
                                                                    ------------
   Net Assets                                                       $668,163,556
                                                                    ============
Composition of Net Assets:
Paid-in-capital                                                     $668,150,206
Accumulated undistributed net investment income                           13,350
                                                                    ------------
   Net Assets                                                       $668,163,556
                                                                    ============
Net Asset Value Per Share
668,163,556 SHARES OUTSTANDING (UNLIMITED SHARES
AUTHORIZED OF $.01 PAR VALUE)                                       $       1.00
                                                                    ============

                       SEE NOTES TO FINANCIAL STATEMENTS


                                        9

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Statement of Operations
FOR THE YEAR ENDED JUNE 30, 2006

Net Investment Income:
Interest Income                                                     $25,130,534
                                                                    -----------
Expenses
Investment advisory fee                                                 590,541
Administration fee                                                      295,270
Registration fees                                                        92,522
Professional fees                                                        66,069
Custodian fees                                                           41,631
Shareholder reports and notices                                          33,011
Trustees' fees and expenses                                               6,490
Transfer agent fees and expenses                                          2,753
Other                                                                    39,391
                                                                    -----------
   Total Expenses                                                     1,167,678
Less: amounts waived                                                   (301,480)
Less: expense offset                                                         (9)
                                                                    -----------
   Net Expenses                                                         866,189
                                                                    -----------
Net Investment Income                                               $24,264,345
                                                                    ===========

                       SEE NOTES TO FINANCIAL STATEMENTS


                                       10

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Statements of Changes in Net Assets

                                                   FOR THE YEAR    FOR THE YEAR
                                                      ENDED           ENDED
                                                  JUNE 30, 2006   JUNE 30, 2005
                                                  -------------   -------------
Increase (Decrease) in Net Assets: Operations:
Net investment income                              $ 24,264,345    $  9,046,363
Dividends to shareholders from net investment
   income                                           (24,264,345)     (9,046,363)
Net increase from transactions in shares of
   beneficial interest                              194,345,903      87,972,258
                                                   ------------    ------------
   Net Increase                                     194,345,903      87,972,258

Net Assets:
Beginning of period                                 473,817,653     385,845,395
                                                   ------------    ------------
End of Period
(INCLUDING ACCUMULATED UNDISTRIBUTED NET
INVESTMENT INCOME OF $13,350 AND $13,350,
RESPECTIVELY)                                      $668,163,556    $473,817,653
                                                   ============    ============

                       SEE NOTES TO FINANCIAL STATEMENTS


                                       11

<Page>

ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST

NOTES TO FINANCIAL STATEMENTS - JUNE 30, 2006

1. ORGANIZATION AND ACCOUNTING POLICIES

Active Assets Institutional Government Securities Trust (the "Fund") is
registered under the Investment Company Act of 1940, as amended (the "Act"), as
a diversified, open-end management investment company. The Fund's investment
objective is high current income, preservation of capital and liquidity. The
Fund was organized as a Massachusetts business trust on January 18, 2002 and
commenced operations on November 4, 2002.

The following is a summary of significant accounting policies:

A. VALUATION OF INVESTMENTS -- Portfolio securities are valued at amortized
cost, which approximates market value, in accordance with Rule 2a-7 under the
Act.

B. ACCOUNTING FOR INVESTMENTS -- Security transactions are accounted for on the
trade date (date the order to buy or sell is executed). Realized gains and
losses on security transactions are determined by the identified cost method.
Discounts are accreted and premiums are amortized over the life of the
respective securities. Interest income is accrued daily.

C. REPURCHASE AGREEMENTS -- The Fund may invest directly with institutions in
repurchase agreements. The Fund's custodian receives the collateral, which is
marked-to-market daily to determine that the value of the collateral does not
decrease below the repurchase price plus accrued interest.

D. FEDERAL INCOME TAX POLICY -- It is the Fund's policy to comply with the
requirements of the Internal Revenue Code applicable to regulated investment
companies and to distribute substantially all of its taxable income to its
shareholders. Accordingly, no federal income tax provision is required.

E. DIVIDENDS AND DISTRIBUTIONS TO SHAREHOLDERS -- The Fund records dividends and
distributions to shareholders as of the close of each business day.

F. USE OF ESTIMATES -- The preparation of financial statements in accordance
with generally accepted accounting principles requires management to make
estimates and assumptions that affect the reported amounts and disclosures.
Actual results could differ from those estimates.

2. INVESTMENT ADVISORY/ ADMINISTRATION AGREEMENTS

Pursuant to an Investment Advisory Agreement with Morgan Stanley Investment
Advisors Inc. (the "Investment Adviser"), the Fund pays the Investment Adviser
an advisory fee, accrued daily and payable monthly, by applying the annual rate
of 0.10% to the net assets of the Fund determined as of the close of each
business day.


                                       12

<Page>

Pursuant to an Administation Agreement with Morgan Stanley Services Company Inc.
(the "Administrator"), an affiliate of the Investment Adviser, the Fund pays an
administration fee, accrued daily and payable monthly, by applying the annual
rate of 0.05% to the Fund's daily net assets.

The Investment Adviser and Administrator have capped the Fund's operating
expenses and waived the compensation provided for in its Investment Advisory and
Administration Agreements with the Fund as follows through April 30, 2007: 0.10%
to the portion of the daily net assets not exceeding $500 million; 0.15% to the
portion of the daily net assets exceeding $500 million but not exceeding $750
million; and 0.20% to the portion of the daily net assets in excess of $750
million.

3. SECURITY TRANSACTIONS AND TRANSACTIONS WITH AFFILIATES

The cost of purchases and proceeds from sales/maturities of portfolio securities
for the year ended June 30, 2006, aggregated $42,936,885,199 and
$42,755,033,173, respectively.

Morgan Stanley Trust, an affiliate of the Investment Adviser and Administrator,
is the Fund's transfer agent.

The Fund has an unfunded Deferred Compensation Plan (the "Compensation Plan")
which allows each independent Trustee to defer payment of all, or a portion, of
the fees he receives for serving on the Board of Trustees. Each eligible Trustee
generally may elect to have the deferred amounts credited with a return equal to
the total return on one or more of the Morgan Stanley funds that are offered as
investment options under the Compensation Plan. Appreciation/depreciation and
distributions received from these investments are recorded with an offsetting
increase/decrease in the deferred compensation obligation and do not affect the
net asset value of the Fund.

4. EXPENSE OFFSET

The expense offset represents a reduction of the transfer agent fees and
expenses for earnings on cash balances maintained by the Fund.


                                       13

<Page>

5. SHARES OF BENEFICIAL INTEREST

Transactions in shares of beneficial interest, at $1.00 per share, were as
follows:

                                                 FOR THE YEAR     FOR THE YEAR
                                                     ENDED            ENDED
                                                 JUNE 30, 2006    JUNE 30, 2005
                                                --------------   --------------
Shares sold                                      3,457,148,199    2,522,056,497
Shares issued in reinvestment of dividends          23,983,023        8,993,767
                                                --------------   --------------
                                                 3,481,131,222    2,531,050,264
Shares redeemed                                 (3,286,785,319)  (2,443,078,006)
                                                --------------   --------------
Net increase in shares outstanding                 194,345,903       87,972,258
                                                ==============   ==============

6. NEW ACCOUNTING PRONOUNCEMENT

In July 2006, the Financial Accounting Standards Board (FASB) issued
Interpretation 48, Accounting for Uncertainty in Income Taxes -- an
interpretation of FASB Statement 109 (FIN 48). FIN 48 clarifies the accounting
for income taxes by prescribing the minimum recognition threshold a tax position
must meet before being recognized in the financial statements. FIN 48 is
effective for fiscal years beginning after December 15, 2006. The Fund will
adopt FIN 48 during 2007 and the impact to the Fund's financial statements, if
any, is currently being assessed.


                                       14

<Page>

ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST

FINANCIAL HIGHLIGHTS

Selected ratios and per share data for a share of beneficial interest
outstanding throughout each period:

<Table>
<Caption>
                                                                            FOR THE PERIOD
                                            FOR THE YEAR ENDED JUNE 30,    NOVEMBER 4, 2002*
                                          ------------------------------        THROUGH
                                            2006       2005       2004       JUNE 30, 2003
                                          --------   --------   --------   -----------------
                                                                 
Selected Per Share Data:
Net asset value, beginning of period      $   1.00   $   1.00   $   1.00     $   1.00
                                          --------   --------   --------     --------

Net income from investment operations        0.041      0.021      0.010        0.008
Less dividends from net investment
income                                      (0.041)    (0.021)    (0.010)+     (0.008)
                                          --------   --------   --------     --------
Net asset value, end of period            $   1.00   $   1.00   $   1.00     $   1.00
                                          ========   ========   ========     ========
Total Return                                  4.15%      2.12%      0.97%        0.82%(1)
Ratios to Average Net Assets(3):
Total expenses (before expense offset)        0.15%      0.10%      0.09%        0.03%(2)
Net investment income                         4.11%      2.15%      0.96%        1.17%(2)
Supplemental Data:
Net assets, end of period, in thousands   $668,164   $473,818   $385,845     $155,363
</Table>

- ----------
*    COMMENCEMENT OF OPERATIONS.

+    INCLUDES CAPITAL GAIN DISTRIBUTION OF LESS THAN $0.001.

(1)  NOT ANNUALIZED.

(2)  ANNUALIZED.

(3)  IF THE FUND HAD BORNE ALL OF ITS EXPENSES THAT WERE REIMBURSED OR WAIVED BY
     THE INVESTMENT ADVISER AND ADMINISTRATOR, THE ANNUALIZED EXPENSE AND NET
     INVESTMENT INCOME RATIOS WOULD HAVE BEEN AS FOLLOWS:

                                NET INVESTMENT
PERIOD ENDED:   EXPENSE RATIO    INCOME RATIO
- -------------   -------------   --------------
JUNE 30, 2006       0.20%           4.06%
JUNE 30, 2005       0.20            2.05
JUNE 30, 2004       0.21            0.84
JUNE 30, 2003       0.47            0.73

                        SEE NOTES TO FINANCIAL STATEMENTS


                                       15

<Page>

ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST

REPORT OF INDEPENDENT REGISTERED PUBLIC ACOUNTING FIRM

To the Shareholders and Board of Trustees of
Active Assets Institutional Government Securities Trust:

We have audited the accompanying statement of assets and liabilities of Active
Assets Institutional Government Securities Trust (the "Fund"), including the
portfolio of investments, as of June 30, 2006, and the related statements of
operations for the year then ended and changes in net assets for each of the two
years in the period then ended, and the financial highlights for each of the
periods presented. These financial statements and financial highlights are the
responsibility of the Fund's management. Our responsibility is to express an
opinion on these financial statements and financial highlights based on our
audits.

We conducted our audits in accordance with the standards of the Public Company
Accounting Oversight Board (United States). Those standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements and financial highlights are free of material misstatement. The Fund
is not required to have, nor were we engaged to perform, an audit of its
internal control over financial reporting. Our audits included consideration of
internal control over financial reporting as a basis for designing audit
procedures that are appropriate in the circumstances, but not for the purpose of
expressing an opinion on the effectiveness of the Fund's internal control over
financial reporting. Accordingly, we express no such opinion. An audit also
includes examining, on a test basis, evidence supporting the amounts and
disclosures in the financial statements, assessing the accounting principles
used and significant estimates made by management, as well as evaluating the
overall financial statement presentation. Our procedures included confirmation
of securities owned as of June 30, 2006, by correspondence with the custodian
and broker. We believe that our audits provide a reasonable basis for our
opinion.

In our opinion, the financial statements and financial highlights referred to
above present fairly, in all material respects, the financial position of Active
Assets Institutional Government Securities Trust as of June 30, 2006, the
results of its operations for the year then ended, the changes in its net assets
for each of the two years in the period then ended, and the financial highlights
for each of the periods presented, in conformity with accounting principles
generally accepted in the United States of America.

Deloitte & Touche LLP
NEW YORK, NEW YORK
AUGUST 22, 2006


                                       16

<Page>

ACTIVE ASSETS INSTITUTIONAL GOVERNMENT SECURITIES TRUST

TRUSTEE AND OFFICER INFORMATION

Independent Trustees:

<Table>
<Caption>
                                                                                    NUMBER OF
                                                                                    PORTFOLIOS
                                             TERM OF                                 IN FUND
                             POSITION(S)   OFFICE AND                                COMPLEX
  NAME, AGE AND ADDRESS OF    HELD WITH     LENGTH OF    PRINCIPAL OCCUPATION(S)     OVERSEEN
    INDEPENDENT TRUSTEE       REGISTRANT  TIME SERVED*    DURING PAST 5 YEARS**   BY TRUSTEE***  OTHER DIRECTORSHIPS HELD BY TRUSTEE
- ---------------------------  -----------  ------------  ------------------------  -------------  -----------------------------------
                                                                                  
Michael Bozic (65)           Trustee      Since         Private Investor;         197            Director of various business
c/o Kramer Levin Naftalis &               April 1994    Chairman of the                          organizations.
Frankel LLP                                             Insurance Committee
Counsel to the Independent                              (since July 2006) and
Trustees                                                Director or Trustee of
1177 Avenue of the Americas                             the Retail Funds (since
New York, NY 10036                                      April 1994) and the
                                                        Institutional Funds
                                                        (since July 2003);
                                                        formerly Vice Chairman
                                                        of Kmart Corporation
                                                        (December 1998-
                                                        October 2000), Chairman
                                                        and Chief Executive
                                                        Officer of Levitz
                                                        Furniture Corporation
                                                        (November 1995-November
                                                        1998) and President
                                                        and Chief Executive
                                                        Officer of Hills
                                                        Department Stores (May
                                                        1991-July 1995);
                                                        formerly variously
                                                        Chairman, Chief
                                                        Executive Officer,
                                                        President and Chief
                                                        Operating Officer
                                                        (1987-1991) of the Sears
                                                        Merchandise Group of
                                                        Sears, Roebuck & Co.

Edwin J. Garn (73)           Trustee      Since         Consultant; Director or   197            Director of Franklin Covey (time
1031 N. Chartwell Court                   January 1993  Trustee of the Retail                    management systems), BMW Bank of
Salt Lake City, UT 84103                                Funds (since                             North America, Inc. (industrial
                                                        January 1993) and the                    loan corporation), Escrow Bank USA
                                                        Institutional Funds                      (industrial loan corporation),
                                                        (since July 2003);                       United Space Alliance (joint
                                                        member of the Utah                       venture between Lockheed Martin and
                                                        Regional Advisory Board                  the Boeing Company) and Nuskin Asia
                                                        of Pacific Corp.                         Pacific (multilevel marketing);
                                                        (utility company);                       member of the board of various
                                                        formerly Managing                        civic and charitable organizations.
                                                        Director of Summit
                                                        Ventures LLC (2000-2004)
                                                        (lobbying and consulting
                                                        firm); United States
                                                        Senator (R-Utah)
                                                        (1974-1992) and
                                                        Chairman, Senate Banking
                                                        Committee (1980-1986),
                                                        Mayor of Salt Lake City,
                                                        Utah (1971-1974),
                                                        Astronaut, Space Shuttle
                                                        Discovery (April 12-19,
                                                        1985), and Vice
                                                        Chairman, Huntsman
                                                        Corporation (chemical
                                                        company).

Wayne E. Hedien (72)         Trustee      Since         Retired; Director or      197            Director of The PMI Group Inc.
c/o Kramer Levin Naftalis                 September     Trustee of the Retail                    (private mortgage insurance);
& Frankel LLP                             1997          Funds (since                             Trustee and Vice Chairman of The
Counsel to the Independent                              September 1997) and the                  Field Museum of Natural History;
Trustees                                                Institutional Funds                      director of various other business
1177 Avenue of the Americas                             (since July 2003);                       and charitable organizations.
New York, NY 10036                                      formerly associated with
                                                        the Allstate Companies
                                                        (1966-1994), most
                                                        recently as Chairman of
                                                        The Allstate Corporation
                                                        (March 1993-
                                                        December 1994) and
                                                        Chairman and Chief
                                                        Executive Officer of its
                                                        wholly-owned
                                                        subsidiary, Allstate
                                                        Insurance Company
                                                        (July 1989-December
                                                        1994).
</Table>


                                       17

<Page>

<Table>
<Caption>
                                                                                    NUMBER OF
                                                                                    PORTFOLIOS
                                             TERM OF                                 IN FUND
                             POSITION(S)   OFFICE AND                                COMPLEX
  NAME, AGE AND ADDRESS OF    HELD WITH     LENGTH OF    PRINCIPAL OCCUPATION(S)     OVERSEEN
    INDEPENDENT TRUSTEE       REGISTRANT  TIME SERVED*    DURING PAST 5 YEARS**   BY TRUSTEE***  OTHER DIRECTORSHIPS HELD BY TRUSTEE
- ---------------------------  -----------  ------------  ------------------------  -------------  -----------------------------------
                                                                                  
Dr. Manuel H. Johnson (57)   Trustee      Since         Senior Partner, Johnson   197            Director of NVR, Inc. (home
c/o Johnson Smick Group,                  July 1991     Smick International,                     construction); Director of KFX
Inc.                                                    Inc., a consulting firm;                 Energy; Director of RBS Greenwich
888 16th Street, NW                                     Chairman of the Audit                    Capital Holdings (financial holding
Suite 740                                               Committee and Director                   company).
Washington, D.C. 20006                                  or Trustee of the Retail
                                                        Funds (since July 1991)
                                                        and the Institutional
                                                        Funds (since July 2003);
                                                        Co-Chairman and a
                                                        founder of the Group of
                                                        Seven Council (G7C), an
                                                        international economic
                                                        commission; formerly
                                                        Vice Chairman of the
                                                        Board of Governors of
                                                        the Federal Reserve
                                                        System and Assistant
                                                        Secretary of the U.S.
                                                        Treasury.

Joseph J. Kearns (63)        Trustee      Since         President, Kearns &       198            Director of Electro Rent
c/o Kearns & Associates LLC               July 2003     Associates LLC                           Corporation (equipment leasing),
PMB754                                                  (investment consulting);                 The Ford Family Foundation, and the
23852 Pacific Coast Highway                             Deputy Chairman of the                   UCLA Foundation.
Malibu, CA 90265                                        Audit Committee and
                                                        Director or Trustee of
                                                        the Retail Funds (since
                                                        July 2003) and the
                                                        Institutional Funds
                                                        (since August 1994);
                                                        previously Chairman of
                                                        the Audit Committee of
                                                        the Institutional Funds
                                                        (October 2001- July
                                                        2003); formerly CFO of
                                                        the J. Paul Getty Trust.

Michael E. Nugent (70)       Chairman     Chairman of   General Partner of        197            None.
c/o Triumph Capital, L.P.    of the       the Board     Triumph Capital, L.P., a
445 Park Avenue              Board        (since July   private investment
New York, NY 10022           and          2006) and     partnership; Chairman of
                             Trustee      Trustee       the Board of the Retail
                                          (since        Funds and Institutional
                                          July 1991)    Funds (since July 2006)
                                                        and Director or Trustee
                                                        of the Retail Funds
                                                        (since July 1991) and
                                                        the Institutional Funds
                                                        (since July 2001);
                                                        formerly Chairman of the
                                                        Insurance Committee
                                                        (July 1991-July 2006)
                                                        and Vice President,
                                                        Bankers Trust Company
                                                        and BT Capital
                                                        Corporation (1984-1988).

Fergus Reid (73)             Trustee      Since         Chairman of Lumelite      198            Trustee and Director of certain
c/o Lumelite Plastics                     July 2003     Plastics Corporation;                    investment companies in the
Corporation                                             Chairman of the                          JPMorgan Funds complex managed
85 Charles Colman Blvd.                                 Governance Committee and                 by J.P. Morgan Investment
Pawling, NY 12564                                       Director or Trustee of                   Management Inc.
                                                        the Retail Funds (since
                                                        July 2003) and the
                                                        Institutional Funds
                                                        (since June 1992).
</Table>


                                       18

<Page>

Interested Trustees:

<Table>
<Caption>
                                                                                    NUMBER OF
                                                                                    PORTFOLIOS
                                             TERM OF                                 IN FUND
                             POSITION(S)   OFFICE AND                                COMPLEX
  NAME, AGE AND ADDRESS OF    HELD WITH     LENGTH OF    PRINCIPAL OCCUPATION(S)     OVERSEEN
     INTERESTED TRUSTEE       REGISTRANT  TIME SERVED*    DURING PAST 5 YEARS**   BY TRUSTEE***  OTHER DIRECTORSHIPS HELD BY TRUSTEE
- ---------------------------  -----------  ------------  ------------------------  -------------  -----------------------------------
                                                                                  
Charles A. Fiumefreddo (73)  Trustee      Since         Director or Trustee of    197            None.
c/o Morgan Stanley Trust                  July 1991     the Retail Funds (since
Harborside Financial Center                             July 1991) and the
Plaza Two                                               Institutional Funds
Jersey City, NJ 07311                                   (since July 2003);
                                                        formerly Chairman of the
                                                        Retail Funds (July 1991-
                                                        July 2006) and the
                                                        Institutional Funds
                                                        (July 2003-July 2006)
                                                        and Chief Executive
                                                        Officer of the Retail
                                                        Funds (until
                                                        September 2002).

James F. Higgins (58)        Trustee      Since         Director or Trustee of    197            Director of AXA Financial, Inc.
c/o Morgan Stanley Trust                  June 2000     the Retail Funds (since                  and The Equitable Life Assurance
Harborside Financial Center                             June 2000) and the                       Society of the United States
Plaza Two                                               Institutional Funds                      (financial services).
Jersey City, NJ 07311                                   (since July  2003);
                                                        Senior Advisor of Morgan
                                                        Stanley (since August
                                                        2000).
</Table>

- ----------
*    THIS IS THE EARLIEST DATE THE TRUSTEE BEGAN SERVING THE FUNDS ADVISED BY
     MORGAN STANLEY INVESTMENT ADVISORS INC. (THE "INVESTMENT ADVISER") (THE
     "RETAIL FUNDS").

**   THE DATES REFERENCED BELOW INDICATING COMMENCEMENT OF SERVICES AS
     DIRECTOR/TRUSTEE FOR THE RETAIL FUNDS AND THE FUNDS ADVISED BY MORGAN
     STANLEY INVESTMENT MANAGEMENT INC. AND MORGAN STANLEY AIP GP LP (THE
     "INSTITUTIONAL FUNDS") REFLECT THE EARLIEST DATE THE DIRECTOR/TRUSTEE BEGAN
     SERVING THE RETAIL OR INSTITUTIONAL FUNDS, AS APPLICABLE.

***  THE FUND COMPLEX INCLUDES ALL OPEN-END AND CLOSED-END FUNDS (INCLUDING ALL
     OF THEIR PORTFOLIOS) ADVISED BY THE INVESTMENT ADVISER AND ANY FUNDS THAT
     HAVE AN INVESTMENT ADVISER THAT IS AN AFFILIATED PERSON OF THE INVESTMENT
     ADVISER (INCLUDING, BUT NOT LIMITED TO, MORGAN STANLEY INVESTMENT
     MANAGEMENT INC.).


                                       19

<Page>

OFFICERS:

<Table>
<Caption>
                                                     TERM OF
                                POSITION(S)        OFFICE AND
  NAME, AGE AND ADDRESS OF       HELD WITH          LENGTH OF
     EXECUTIVE OFFICER           REGISTRANT        TIME SERVED*            PRINCIPAL OCCUPATION(S)DURING PAST 5 YEARS**
- ---------------------------   ---------------   -----------------   -----------------------------------------------------------
                                                           
Ronald E. Robison (67)        President and     President (since    President (since September 2005) and Principal Executive
1221 Avenue of the Americas   Principal         September 2005)     Officer (since May 2003) of funds in the Fund Complex;
New York, NY 10020            Executive         and Principal       President (since September 2005) and Principal Executive
                              Officer           Executive Officer   Officer (since May 2003) of the Van Kampen Funds; Managing
                                                (since May 2003)    Director, Director and/or Officer of the Investment
                                                                    Adviser and various entities affiliated with the
                                                                    Investment Adviser; Director of Morgan Stanley SICAV
                                                                    (since May 2004). Formerly, Executive Vice President
                                                                    (July 2003 to September 2005) of funds in the Fund Complex
                                                                    and the Van Kampen Funds; President and Director of the
                                                                    Institutional Funds (March 2001 to July 2003); Chief Global
                                                                    Operating Officer of Morgan Stanley Investment Management
                                                                    Inc.; Chief Administrative Officer of Morgan Stanley
                                                                    Investment Advisors Inc.; Chief Administrative Officer of
                                                                    Morgan Stanley Services Company Inc.

J. David Germany (51)         Vice President    Since               Managing Director and (since December 2005) Chief
Morgan Stanley                                  February 2006       Investment Officer - Global Fixed Income of Morgan
Investment Management Ltd.                                          Stanley Investment Management; Managing Director and
25 Cabot Square                                                     Director of Morgan Stanley Investment Management Ltd.;
Canary Wharf, London                                                Vice President (since February 2006) of the Retail and
United Kingdom E144QA                                               Institutional Funds.

Dennis F. Shea (53)           Vice President    Since               Managing Director and (since February 2006) Chief
1221 Avenue of the Americas                     February 2006       Investment Officer - Global Equity of Morgan Stanley
New York, NY 10020                                                  Investment Management; Vice President (since
                                                                    February 2006) of the Retail and Institutional Funds.
                                                                    Formerly, Managing Director and Director of Global Equity
                                                                    Research at Morgan Stanley.

Barry Fink (51)               Vice President    Since               Managing Director and General Counsel of Morgan Stanley
1221 Avenue of the Americas                     February 1997       Investment Management; Managing Director of the
New York, NY 10020                                                  Investment Adviser and various entities affiliated with
                                                                    the Investment Adviser; Vice President of the Retail
                                                                    Funds and (since July 2003) the Institutional Funds.
                                                                    Formerly, Secretary, General Counsel and/or Director of
                                                                    the Investment Adviser and various entities affiliated
                                                                    with the Investment Adviser; Secretary and General
                                                                    Counsel of the Retail Funds.

Amy R. Doberman (44)          Vice President    Since July 2004     Managing Director and General Counsel, U.S. Investment
1221 Avenue of the Americas                                         Management of Morgan Stanley Investment Management (since
New York, NY 10020                                                  July 2004); Vice President of the Retail Funds and the
                                                                    Institutional Funds (since July 2004); Vice President of
                                                                    the Van Kampen Funds (since August 2004); Secretary (since
                                                                    February 2006) and Managing Director (since July 2004) of
                                                                    the Investment Adviser and various entities affiliated
                                                                    with the Investment Adviser. Formerly, Managing Director
                                                                    and General Counsel - Americas, UBS Global Asset
                                                                    Management (July 2000 to July 2004).

Carsten Otto (42)             Chief             Since October       Managing Director and U.S. Director of Compliance for
1221 Avenue of the Americas   Compliance        2004                Morgan Stanley Investment Management (since October 2004);
New York, NY 10020            Officer                               Managing Director and Chief Compliance Officer of Morgan
                                                                    Stanley Investment Management. Formerly, Assistant
                                                                    Secretary and Assistant General Counsel of the Retail
                                                                    Funds.
</Table>


                                       20

<Page>

<Table>
<Caption>
                                                     TERM OF
                                POSITION(S)        OFFICE AND
  NAME, AGE AND ADDRESS OF       HELD WITH          LENGTH OF
     EXECUTIVE OFFICER           REGISTRANT        TIME SERVED*            PRINCIPAL OCCUPATION(S)DURING PAST 5 YEARS**
- ---------------------------   ---------------   -----------------   -----------------------------------------------------------
                                                           
Stefanie V. Chang Yu (39)     Vice President    Since July 2003     Executive Director of the Investment Adviser and various
1221 Avenue of the Americas                                         entities affiliated with the Investment Adviser; Vice
New York, NY 10020                                                  President of the Retail Funds (since July 2002) and the
                                                                    Institutional Funds (since December 1997). Formerly,
                                                                    Secretary of various entities affiliated with the
                                                                    Investment Adviser.

Francis J. Smith (40)         Treasurer and     Treasurer (since    Executive Director of the Investment Adviser and various
c/o Morgan Stanley Trust      Chief Financial   July 2003) and      entities affiliated with the Investment Adviser;
Harborside Financial Center   Officer           Chief Financial     Treasurer and Chief Financial Officer of the Retail Funds
Plaza Two                                       Officer (since      (since July 2003). Formerly, Vice President of the Retail
Jersey City, NJ 07311                           September 2002)     Funds (September 2002 to July 2003).

Mary E. Mullin (39)           Secretary         Since July 2003     Executive Director of the Investment Adviser and various
1221 Avenue of the Americas                                         entities affiliated with the Investment Adviser;
New York, NY 10020                                                  Secretary of the Retail Funds (since July 2003) and the
                                                                    Institutional Funds (since June 1999).
</Table>

- ----------
*    THIS IS THE EARLIEST DATE THE OFFICER BEGAN SERVING THE RETAIL FUNDS. EACH
     OFFICER SERVES AN INDEFINITE TERM, UNTIL HIS OR HER SUCCESSOR IS ELECTED.

**   THE DATES REFERENCED BELOW INDICATING COMMENCEMENT OF SERVICE AS AN OFFICER
     FOR THE RETAIL AND INSTITUTIONAL FUNDS REFLECT THE EARLIEST DATE THE
     OFFICER BEGAN SERVING THE RETAIL OR INSTITUTIONAL FUNDS, AS APPLICABLE.

                       2006 FEDERAL TAX NOTICE (UNAUDITED)

Of the Fund's ordinary dividends paid during the fiscal year ended June 30,
2006, 52.39% was attributable to qualifying Federal obligations. Please consult
your tax advisor to determine if any portion of the dividends you received is
exempt from state income tax.


                                       21

<Page>

                 (This page has been left blank intentionally.)

<Page>

                 (This page has been left blank intentionally.)

<Page>

TRUSTEES
Michael Bozic
Charles A. Fiumefreddo
Edwin J. Garn
Wayne E. Hedien
James F. Higgins
Dr. Manuel H. Johnson
Joseph J. Kearns
Michael E. Nugent
Fergus Reid

OFFICERS
Michael E. Nugent
CHAIRMAN OF THE BOARD

Ronald E. Robison
PRESIDENT AND PRINCIPAL EXECUTIVE OFFICER

J. David Germany
VICE PRESIDENT

Dennis F. Shea
VICE PRESIDENT

Barry Fink
VICE PRESIDENT

Amy R. Doberman
VICE PRESIDENT

Carsten Otto
CHIEF COMPLIANCE OFFICER

Stefanie V. Chang Yu
VICE PRESIDENT

Francis J. Smith
TREASURER AND CHIEF FINANCIAL OFFICER

Mary E. Mullin
SECRETARY

TRANSFER AGENT
Morgan Stanley Trust
Harborside Financial Center, Plaza Two
Jersey City, New Jersey 07311

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
Deloitte & Touche LLP
Two World Financial Center
New York, New York 10281

INVESTMENT ADVISER
Morgan Stanley Investment Advisors Inc.
1221 Avenue of the Americas
New York, New York 10020

This report is submitted for the general information of the shareholders of the
Fund. For more detailed information about the Fund, its fees and expenses and
other pertinent information, please read its Prospectus. The Fund's Statement of
Additional Information contains additional information about the Fund, including
its trustees. It is available, without charge, by calling (800) 869-NEWS.

This report is not authorized for distribution to prospective investors in the
Fund unless preceded or accompanied by an effective Prospectus. Read the
Prospectus carefully before investing.

Investments and services offered through Morgan Stanley DW Inc., member SIPC.

(C) 2006 Morgan Stanley

[Morgan Stanley LOGO]

MORGAN STANLEY FUNDS

Active Assets
Institutional
Government
Securities Trust

Annual Report
June 30, 2006

[Morgan Stanley LOGO]
AISRPT-RA06-00725P-Y06/06
<Page>

Item 2. Code of Ethics.

(a) The Fund has adopted a code of ethics (the "Code of Ethics") that applies to
its principal executive officer, principal financial officer, principal
accounting officer or controller, or persons performing similar functions,
regardless of whether these individuals are employed by the Fund or a third
party.

(b) No information need be disclosed pursuant to this paragraph.

(c) Not applicable.

(d) Not applicable.

(e) Not applicable.

(f)

     (1) The Fund's Code of Ethics is attached hereto as Exhibit 12 A.

     (2) Not applicable.

     (3) Not applicable.

Item 3. Audit Committee Financial Expert.

The Fund's Board of Trustees has determined that it has two "audit committee
financial experts" serving on its audit committee, each of whom are
"independent" Trustees: Dr. Manuel H. Johnson and Joseph J. Kearns. Under
applicable securities laws, a person who is determined to be an audit committee
financial expert will not be deemed an "expert" for any purpose, including
without limitation for the purposes of Section 11 of the Securities Act of 1933,
as a result of being designated or identified as an audit committee financial
expert. The designation or identification of a person as an audit committee
financial expert does not impose on such person any duties, obligations, or
liabilities that are greater than the duties, obligations, and liabilities
imposed on such person as a member of the audit committee and Board of Trustees
in the absence of such designation or identification.

<Page>

Item 4. Principal Accountant Fees and Services.

(a)(b)(c)(d) and (g). Based on fees billed for the periods shown:

2006

                                 REGISTRANT     COVERED ENTITIES(1)
                                 ----------     -------------------
   AUDIT FEES                      $26,320              N/A
   NON-AUDIT FEES
      AUDIT-RELATED FEES           $   531 (2)     $5,190,300 (2)
      TAX FEES                     $ 5,000 (3)     $2,044,491 (4)
      ALL OTHER FEES               $    --         $       --
   TOTAL NON-AUDIT FEES            $ 5,531         $7,234,791

   TOTAL                           $31,851         $7,234,791

2005

                                 REGISTRANT     COVERED ENTITIES(1)
                                 ----------     -------------------
   AUDIT FEES                      $26,465              N/A
   NON-AUDIT FEES
      AUDIT-RELATED FEES           $   540 (2)     $3,215,745 (2)
      TAX FEES                     $ 4,948 (3)     $   24,000 (4)
      ALL OTHER FEES               $    --         $       --
   TOTAL NON-AUDIT FEES            $ 5,488         $3,239,745
   TOTAL                           $31,953         $3,239,745

N/A- Not applicable, as not required by Item 4.

(1)  Covered Entities include the Adviser (excluding sub-advisors) and any
     entity controlling, controlled by or under common control with the Adviser
     that provides ongoing services to the Registrant.

(2)  Audit-Related Fees represent assurance and related services provided that
     are reasonably related to the performance of the audit of the financial
     statements of the Covered Entities' and funds advised by the Adviser or its
     affiliates, specifically data verification and agreed-upon procedures
     related to asset securitizations and agreed-upon procedures engagements.

(3)  Tax Fees represent tax compliance, tax planning and tax advice services
     provided in connection with the preparation and review of the Registrant's
     tax returns.

(4)  Tax Fees represent tax compliance, tax planning and tax advice services
     provided in connection with the review of Covered Entities' tax returns.

(5)  All other fees represent project management for future business
     applications and improving business and operational processes.

<Page>

(e)(1) The audit committee's pre-approval policies and procedures are as
follows:

                                                                      APPENDIX A

                                 AUDIT COMMITTEE
                          AUDIT AND NON-AUDIT SERVICES
                       PRE-APPROVAL POLICY AND PROCEDURES
                                     OF THE
                  MORGAN STANLEY RETAIL AND INSTITUTIONAL FUNDS

                    AS ADOPTED AND AMENDED JULY 23, 2004,(1)

     1. STATEMENT OF PRINCIPLES

The Audit Committee of the Board is required to review and, in its sole
discretion, pre-approve all Covered Services to be provided by the Independent
Auditors to the Fund and Covered Entities in order to assure that services
performed by the Independent Auditors do not impair the auditor's independence
from the Fund.

The SEC has issued rules specifying the types of services that an independent
auditor may not provide to its audit client, as well as the audit committee's
administration of the engagement of the independent auditor. The SEC's rules
establish two different approaches to pre-approving services, which the SEC
considers to be equally valid. Proposed services either: may be pre-approved
without consideration of specific case-by-case services by the Audit Committee
("GENERAL PRE-APPROVAL"); or require the specific pre-approval of the Audit
Committee or its delegate ("SPECIFIC PRE-APPROVAL"). The Audit Committee
believes that the combination of these two approaches in this Policy will result
in an effective and efficient procedure to pre-approve services performed by the
Independent Auditors. As set forth in this Policy, unless a type of service has
received general pre-approval, it will require specific pre-approval by the
Audit Committee (or by any member of the Audit Committee to which pre-approval
authority has been delegated) if it is to be provided by the Independent
Auditors. Any proposed services exceeding pre-approved cost levels or budgeted
amounts will also require specific pre-approval by the Audit Committee.

The appendices to this Policy describe the Audit, Audit-related, Tax and All
Other services that have the general pre-approval of the Audit Committee. The
term of any general pre-approval is 12 months from the date of pre-approval,
unless the Audit Committee considers and provides a different period and states
otherwise. The Audit Committee will annually review and pre-approve the services
that may be provided by the Independent Auditors without obtaining specific
pre-approval from the Audit Committee. The Audit Committee will add to or
subtract from the list of general pre-approved services from time to time, based
on subsequent determinations.

- ----------
(1)  This Audit Committee Audit and Non-Audit Services Pre-Approval Policy and
     Procedures (the "POLICY"), adopted as of the date above, supersedes and
     replaces all prior versions that may have been adopted from time to time.

<Page>

The purpose of this Policy is to set forth the policy and procedures by which
the Audit Committee intends to fulfill its responsibilities. It does not
delegate the Audit Committee's responsibilities to pre-approve services
performed by the Independent Auditors to management.

The Fund's Independent Auditors have reviewed this Policy and believes that
implementation of the Policy will not adversely affect the Independent Auditors'
independence.

     2. DELEGATION

As provided in the Act and the SEC's rules, the Audit Committee may delegate
either type of pre-approval authority to one or more of its members. The member
to whom such authority is delegated must report, for informational purposes
only, any pre-approval decisions to the Audit Committee at its next scheduled
meeting.

     3. AUDIT SERVICES

The annual Audit services engagement terms and fees are subject to the specific
pre-approval of the Audit Committee. Audit services include the annual financial
statement audit and other procedures required to be performed by the Independent
Auditors to be able to form an opinion on the Fund's financial statements. These
other procedures include information systems and procedural reviews and testing
performed in order to understand and place reliance on the systems of internal
control, and consultations relating to the audit. The Audit Committee will
approve, if necessary, any changes in terms, conditions and fees resulting from
changes in audit scope, Fund structure or other items.

In addition to the annual Audit services engagement approved by the Audit
Committee, the Audit Committee may grant general pre-approval to other Audit
services, which are those services that only the Independent Auditors reasonably
can provide. Other Audit services may include statutory audits and services
associated with SEC registration statements (on Forms N-1A, N-2, N-3, N-4,
etc.), periodic reports and other documents filed with the SEC or other
documents issued in connection with securities offerings.

The Audit Committee has pre-approved the Audit services in Appendix B.1. All
other Audit services not listed in Appendix B.1 must be specifically
pre-approved by the Audit Committee (or by any member of the Audit Committee to
which pre-approval has been delegated).

     4. AUDIT-RELATED SERVICES

Audit-related services are assurance and related services that are reasonably
related to the performance of the audit or review of the Fund's financial
statements and, to the extent they are Covered Services, the Covered Entities or
that are traditionally performed by the Independent Auditors. Because the Audit
Committee believes that the provision of Audit-related services does not impair
the independence of the auditor and is consistent with the SEC's rules on
auditor independence, the Audit Committee may grant general pre-approval to
Audit-related services. Audit-related services include, among others, accounting
consultations related to accounting, financial reporting or disclosure matters

<Page>

not classified as "Audit services"; assistance with understanding and
implementing new accounting and financial reporting guidance from rulemaking
authorities; agreed-upon or expanded audit procedures related to accounting
and/or billing records required to respond to or comply with financial,
accounting or regulatory reporting matters; and assistance with internal control
reporting requirements under Forms N-SAR and/or N-CSR.

The Audit Committee has pre-approved the Audit-related services in Appendix B.2.
All other Audit-related services not listed in Appendix B.2 must be specifically
pre-approved by the Audit Committee (or by any member of the Audit Committee to
which pre-approval has been delegated).

     5. TAX SERVICES

The Audit Committee believes that the Independent Auditors can provide Tax
services to the Fund and, to the extent they are Covered Services, the Covered
Entities, such as tax compliance, tax planning and tax advice without impairing
the auditor's independence, and the SEC has stated that the Independent Auditors
may provide such services.

Pursuant to the preceding paragraph, the Audit Committee has pre-approved the
Tax Services in Appendix B.3. All Tax services in Appendix B.3 must be
specifically pre-approved by the Audit Committee (or by any member of the Audit
Committee to which pre-approval has been delegated).

     6. ALL OTHER SERVICES

The Audit Committee believes, based on the SEC's rules prohibiting the
Independent Auditors from providing specific non-audit services, that other
types of non-audit services are permitted. Accordingly, the Audit Committee
believes it may grant general pre-approval to those permissible non-audit
services classified as All Other services that it believes are routine and
recurring services, would not impair the independence of the auditor and are
consistent with the SEC's rules on auditor independence.

The Audit Committee has pre-approved the All Other services in Appendix B.4.
Permissible All Other services not listed in Appendix B.4 must be specifically
pre-approved by the Audit Committee (or by any member of the Audit Committee to
which pre-approval has been delegated).

     7. PRE-APPROVAL FEE LEVELS OR BUDGETED AMOUNTS

Pre-approval fee levels or budgeted amounts for all services to be provided by
the Independent Auditors will be established annually by the Audit Committee.
Any proposed services exceeding these levels or amounts will require specific
pre-approval by the Audit Committee. The Audit Committee is mindful of the
overall relationship of fees for audit and non-audit services in determining
whether to pre-approve any such services.

     8. PROCEDURES

All requests or applications for services to be provided by the Independent
Auditors that do not require specific approval by the Audit Committee will be
submitted to the Fund's Chief Financial Officer and must include a detailed
description of the services to be

<Page>

rendered. The Fund's Chief Financial Officer will determine whether such
services are included within the list of services that have received the general
pre-approval of the Audit Committee. The Audit Committee will be informed on a
timely basis of any such services rendered by the Independent Auditors. Requests
or applications to provide services that require specific approval by the Audit
Committee will be submitted to the Audit Committee by both the Independent
Auditors and the Fund's Chief Financial Officer, and must include a joint
statement as to whether, in their view, the request or application is consistent
with the SEC's rules on auditor independence.

The Audit Committee has designated the Fund's Chief Financial Officer to monitor
the performance of all services provided by the Independent Auditors and to
determine whether such services are in compliance with this Policy. The Fund's
Chief Financial Officer will report to the Audit Committee on a periodic basis
on the results of its monitoring. Both the Fund's Chief Financial Officer and
management will immediately report to the chairman of the Audit Committee any
breach of this Policy that comes to the attention of the Fund's Chief Financial
Officer or any member of management.

     9. ADDITIONAL REQUIREMENTS

The Audit Committee has determined to take additional measures on an annual
basis to meet its responsibility to oversee the work of the Independent Auditors
and to assure the auditor's independence from the Fund, such as reviewing a
formal written statement from the Independent Auditors delineating all
relationships between the Independent Auditors and the Fund, consistent with
Independence Standards Board No. 1, and discussing with the Independent Auditors
its methods and procedures for ensuring independence.

     10. COVERED ENTITIES

Covered Entities include the Fund's investment adviser(s) and any entity
controlling, controlled by or under common control with the Fund's investment
adviser(s) that provides ongoing services to the Fund(s). Beginning with
non-audit service contracts entered into on or after May 6, 2003, the Fund's
audit committee must pre-approve non-audit services provided not only to the
Fund but also to the Covered Entities if the engagements relate directly to the
operations and financial reporting of the Fund. This list of Covered Entities
would include:

          MORGAN STANLEY RETAIL FUNDS
          Morgan Stanley Investment Advisors Inc.
          Morgan Stanley & Co. Incorporated
          Morgan Stanley DW Inc.
          Morgan Stanley Investment Management Inc.
          Morgan Stanley Investment Management Limited
          Morgan Stanley Investment Management Private Limited
          Morgan Stanley Asset & Investment Trust Management Co., Limited
          Morgan Stanley Investment Management Company
          Van Kampen Asset Management
          Morgan Stanley Services Company, Inc.
          Morgan Stanley Distributors Inc.
          Morgan Stanley Trust FSB

<Page>

          MORGAN STANLEY INSTITUTIONAL FUNDS
          Morgan Stanley Investment Management Inc.
          Morgan Stanley Investment Advisors Inc.
          Morgan Stanley Investment Management Limited
          Morgan Stanley Investment Management Private Limited
          Morgan Stanley Asset & Investment Trust Management Co., Limited
          Morgan Stanley Investment Management Company
          Morgan Stanley & Co. Incorporated
          Morgan Stanley Distribution, Inc.
          Morgan Stanley AIP GP LP
          Morgan Stanley Alternative Investment Partners LP

(e)(2) Beginning with non-audit service contracts entered into on or after May
6, 2003, the audit committee also is required to pre-approve services to Covered
Entities to the extent that the services are determined to have a direct impact
on the operations or financial reporting of the Registrant. 100% of such
services were pre-approved by the audit committee pursuant to the Audit
Committee's pre-approval policies and procedures (attached hereto).

(f) Not applicable.

(g) See table above.

(h) The audit committee of the Board of Trustees has considered whether the
provision of services other than audit services performed by the auditors to the
Registrant and Covered Entities is compatible with maintaining the auditors'
independence in performing audit services.

Item 5. Audit Committee of Listed Registrants.

(a) The Fund has a separately-designated standing audit committee established in
accordance with Section 3(a)(58)(A) of the Exchange Act whose members are:
Michael Bozic, Edwin J. Garn, Wayne E. Hedien, Manual H. Johnson, Joseph J.
Kearns, Michael Nugent and Fergus Reid.

(b) Not applicable.

Item 6. Schedule of Investments

Refer to Item 1.

<Page>

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End
Management Investment Companies.

Applicable only to reports filed by closed-end funds.

Item 8. Portfolio Managers of Closed-End Management Investment Companies

Applicable only to reports filed by closed-end funds.

Item 9. Closed-End Fund Repurchases

Applicable only to reports filed by closed-end funds.

Item 10. Submission of Matters to a Vote of Security Holders

Not applicable.

Item 11. Controls and Procedures

(a) The Fund's principal executive officer and principal financial officer have
concluded that the Fund's disclosure controls and procedures are sufficient to
ensure that information required to be disclosed by the Fund in this Form N-CSR
was recorded, processed, summarized and reported within the time periods
specified in the Securities and Exchange Commission's rules and forms, based
upon such officers' evaluation of these controls and procedures as of a date
within 90 days of the filing date of the report.

(b) There were no changes in the registrant's internal control over financial
reporting that occurred during the second fiscal quarter of the period covered
by this report that has materially affected, or is reasonably likely to
materially affect, the registrant's internal control over financial reporting.

Item 12. Exhibits

(a) The Code of Ethics for Principal Executive and Senior Financial Officers is
attached hereto.

(b) A separate certification for each principal executive officer and principal
financial officer of the registrant are attached hereto as part of EX-99.CERT.
<Page>

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, the registrant has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.

Active Assets Institutional Government Securities Trust


/s/ Ronald E. Robison
- ---------------------------
Ronald E. Robison
Principal Executive Officer
August 10, 2006

     Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, this report has been signed by the following
persons on behalf of the registrant and in the capacities and on the dates
indicated.


/s/ Ronald E. Robison
- ---------------------------
Ronald E. Robison
Principal Executive Officer
August 10, 2006


/s/ Francis Smith
- ---------------------------
Francis Smith
Principal Financial Officer
August 10, 2006