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: 811-03165

Active Assets 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: December 31, 2005

Item 1 - Report to Shareholders

Welcome, Shareholder:

In this report, you'll learn about how your investment in Active Assets
Government Securities Trust performed during the semiannual 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.

FUND REPORT

For the six months ended December 31, 2005

MARKET CONDITIONS

During the six-month period ended December 31, 2005, the Federal Open Market
Committee (the "Fed") continued its pattern of raising short-term rates begun in
June of 2004. Through 13 steps of 25 basis points each -- including four during
the six months covered by this report -- the Fed increased its target rate for
federal funds to 4.25 percent.

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

PERFORMANCE ANALYSIS

As of December 31, 2005, Active Assets Government Securities Trust had net
assets of approximately $738 million and an average portfolio maturity of 27
days. For the six-month period ended December 31, 2005, the Fund provided a
total return of 1.56 percent. For the seven-day period ended December 31, 2005,
the Fund provided an effective annualized yield of 3.65 percent and a current
yield of 3.59 percent, while its 30-day moving average yield for December was
3.52 percent. Past performance is no guarantee of future results.

Our strategy in managing the Fund remained consistent with the Fund's long-term
focus on maintaining preservation of capital and liquidity. By shortening the
maturities of the portfolio's investments slightly, we were able to reinvest in
higher yielding money market securities as rates climbed. We adhered to a
conservative approach in managing the Fund that emphasized purchasing
high-quality money market obligations 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 well
or that securities in such sectors will be held by the Fund in the future.

<Table>
<Caption>
PORTFOLIO COMPOSITION

U.S. Government Agencies -- Discount Notes 86.0%
Repurchase Agreements 12.9
U.S. Government Agencies -- Floating Rate Notes 1.1
</Table>

<Table>
<Caption>
MATURITY SCHEDULE

1 -- 30 Days 69.8%
31 -- 60 Days 22.9
61 -- 90 Days 4.9
91 -- 120 Days 2.4
</Table>

Data as of December 31, 2005. 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.

INVESTMENT STRATEGY

THE FUND WILL INVEST IN HIGH QUALITY, SHORT-TERM U.S. GOVERNMENT SECURITIES. 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 BY FILING THE SCHEDULE ELECTRONICALLY WITH THE
SECURITIES AND EXCHANGE COMMISSION (SEC). THE SEMIANNUAL REPORTS ARE FILED ON
FORM N-CSRS AND THE ANNUAL REPORTS ARE FILED ON FORM N-CSR. 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.

EXPENSE EXAMPLE

As a shareholder of the Fund, you incur ongoing costs, including advisory fees;
distribution and service (12b-1) 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 07/01/05 -- 12/31/05.

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 *
------------- ------------- ---------------
07/01/05 -
07/01/05 12/31/05 12/31/05
------------- ------------- ---------------

Actual (1.56% return)....................................... $1,000.00 $1,015.60 $2.98
Hypothetical (5% annual return before expenses)............. $1,000.00 $1,022.11 $2.99
</Table>

- ------------------

* Expenses are equal to the Fund's annualized expense ratio of 0.59%
multiplied by the average account value over the period, multiplied by
183/365 (to reflect the one-half year period).

Active Assets Government Securities Trust
PORTFOLIO OF INVESTMENTS - DECEMBER 31, 2005 (UNAUDITED)

<Table>
<Caption>
ANNUALIZED
PRINCIPAL YIELD
AMOUNT IN ON DATE OF MATURITY
THOUSANDS DESCRIPTION PURCHASE DATES VALUE
- ----------------------------------------------------------------------------------------------------------

U.S. Government Agencies - Discount Notes (83.4%)
$465,972 Federal Home Loan Banks...................... 4.12 - 4.36% 01/04/06-03/22/06 $464,787,499
27,759 Federal National Mortgage Assoc.............. 4.28 - 4.41 02/22/06-04/19/06 27,462,677
123,968 Freddie Mac.................................. 3.97 - 4.34 01/10/06-03/14/06 123,331,525
------------
Total U.S. Government Agencies - Discount Notes (Cost $615,581,701)............ 615,581,701
------------
Repurchase Agreements (12.5%)
12,300 Banc of America Securities, LLC
(dated 12/30/05; proceeds $12,305,836)
(a)........................................ 4.27 01/03/06 12,300,000
80,000 Goldman Sachs & Co.
(dated 12/27/05; proceeds $80,066,733)
(b)........................................ 4.29 01/03/06 80,000,000
------------
Total Repurchase Agreements (Cost $92,300,000)................................. 92,300,000
------------
U.S. Government Agencies - Floating Rate Notes (1.1%)
3,100 Federal Farm Credit Banks.................... 4.24+ 01/03/06* 3,101,319
5,000 Federal Home Loan Banks...................... 4.36+ 03/13/06* 4,999,922
------------
Total U.S. Government Agencies - Floating Rate Notes (Cost $8,101,241)......... 8,101,241
------------
</Table>

<Table>

Total Investments (Cost $715,982,942) (c)....................... 97.0% 715,982,942

Other Assets in Excess of Liabilities........................... 3.0 22,173,926
----- ------------
Net Assets...................................................... 100.0% $738,156,868
===== ============
</Table>

- ---------------------

<Table>

* Date of next interest rate reset.
+ Rate shown is the rate in effect at December 31, 2005.
(a) Collateralized by Federal National Mortgage Assoc. 5.00% due
08/01/35 valued at $12,546,000.
(b) Collateralized by Feddie Mac 4.00% - 7.50% due
03/01/19 - 12/01/34 valued at $81,600,000.
(c) Cost is the same for federal income tax purposes.
</Table>

See Notes to Financial Statements
6

Active Assets Government Securities Trust
FINANCIAL STATEMENTS

Statement of Assets and Liabilities
December 31, 2005 (unaudited)

<Table>

Assets:
Investments in securities, at value (cost $715,982,942)
(including repurchase agreements of $92,300,000).......... $715,982,942
Cash........................................................ 35,885
Receivable for:
Shares of beneficial interest sold...................... 22,544,366
Interest................................................ 60,706
Prepaid expenses and other assets........................... 33,562
------------
Total Assets............................................ 738,657,461
------------
Liabilities:
Payable for:
Investment advisory fee................................. 286,044
Distribution fee........................................ 69,055
Administration fee...................................... 34,528
Accrued expenses and other payables......................... 110,966
------------
Total Liabilities....................................... 500,593
------------
Net Assets.............................................. $738,156,868
============
Composition of Net Assets:
Paid-in-capital............................................. $738,112,105
Accumulated undistributed net investment income............. 44,763
------------
Net Assets.............................................. $738,156,868
============
Net Asset Value Per Share
738,156,410 shares outstanding (unlimited shares authorized
of $.01 par value).......................................... $1.00
============
</Table>

See Notes to Financial Statements
7

Active Assets Government Securities Trust
FINANCIAL STATEMENTS continued

Statement of Operations
For the six months ended December 31, 2005 (unaudited)

<Table>

Net Investment Income:
Interest Income............................................. $18,039,206
-----------
Expenses
Investment advisory fee..................................... 1,979,563
Distribution fee............................................ 494,740
Administration fee.......................................... 247,370
Transfer agent fees and expenses............................ 59,411
Professional fees........................................... 40,520
Custodian fees.............................................. 24,459
Registration fees........................................... 23,955
Shareholder reports and notices............................. 15,320
Trustees' fees and expenses................................. 10,105
Other....................................................... 27,086
-----------
Total Expenses.......................................... 2,922,529
-----------
Net Investment Income................................... 15,116,677
Net Realized Gain....................................... 1,864
-----------
Net Increase................................................ $15,118,541
===========
</Table>

See Notes to Financial Statements
8

Active Assets Government Securities Trust
FINANCIAL STATEMENTS continued

Statement of Changes in Net Assets

<Table>
<Caption>
FOR THE SIX FOR THE YEAR
MONTHS ENDED ENDED
DECEMBER 31, 2005 JUNE 30, 2005
----------------- --------------
(unaudited)

Increase (Decrease) in Net Assets:
Operations:
Net investment income....................................... $ 15,116,677 $ 17,575,524
Net realized gain........................................... 1,864 988
-------------- --------------
Net Increase............................................ 15,118,541 17,576,512
-------------- --------------
Dividends and Distributions to Shareholders from:
Net investment income....................................... (15,116,550) (17,576,043)
Net realized gain........................................... (1,864) (988)
-------------- --------------
Total Dividends and Distributions....................... (15,118,414) (17,577,031)
-------------- --------------

Net decrease from transactions in shares of beneficial
interest.................................................. (312,027,208) (33,016,332)
-------------- --------------
Net Decrease............................................ (312,027,081) (33,016,851)
Net Assets:
Beginning of period......................................... 1,050,183,949 1,083,200,800
-------------- --------------
End of Period
(Including accumulated undistributed net investment income
of $44,763 and $44,636, respectively)....................... $ 738,156,868 $1,050,183,949
============== ==============
</Table>

See Notes to Financial Statements
9

Active Assets Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2005 (UNAUDITED)

1. Organization and Accounting Policies

Active Assets 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 objectives are
high current income, preservation of capital and liquidity. The Fund was
organized as a Massachusetts business trust on March 30, 1981 and commenced
operations on July 7, 1981.

The following is a summary of significant accounting policies:

A. Valuation of Investments -- Portfolio securities are valued at amortized
cost, which approximates market value.

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 following
annual rates to the net assets of the Fund determined as of the close of each
business day: 0.45% to the portion of the daily net assets not exceeding $500
million; 0.375% to the portion of the daily net assets exceeding $500 million
but not

Active Assets Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2005 (UNAUDITED) continued

exceeding $750 million; 0.325% to the portion of the daily net assets exceeding
$750 million but not exceeding $1 billion; 0.30% to the portion of the daily net
assets exceeding $1 billion but not exceeding $1.5 billion; 0.275% to the
portion of the daily net assets exceeding $1.5 billion but not exceeding $2
billion; 0.25% to the portion of the daily net assets exceeding $2 billion but
not exceeding $2.5 billion; 0.225% to the portion of the daily net assets
exceeding $2.5 billion but not exceeding $3 billion; and 0.20% to the portion of
the daily net assets exceeding $3 billion.

Pursuant to an Administration 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.

3. Plan of Distribution

Morgan Stanley Distributors Inc. (the "Distributor"), an affiliate of the
Investment Adviser and Administrator, is the distributor of the Fund's shares
and in accordance with a Plan of Distribution (the "Plan") pursuant to Rule
12b-1 under the Act, finances certain expenses in connection with the promotion
of sales of Fund shares.

Reimbursements for these expenses are made in monthly payments by the Fund to
the Distributor, which will in no event exceed an amount equal to a payment at
the annual rate of 0.15% of the Fund's average daily net assets during the
month. Expenses incurred by the Distributor pursuant to the Plan in any fiscal
year will not be reimbursed by the Fund through payments accrued in any
subsequent fiscal year. For the six months ended December 31, 2005, the
distribution fee was accrued at the annual rate of 0.10%.

4. Security Transactions and Transactions with Affiliates

The cost of purchases and proceeds from sales/maturities of portfolio securities
for the six months ended December 31, 2005, aggregated $16,433,461,641 and
$16,779,643,326, respectively.

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

The Fund has an unfunded noncontributory defined benefit pension plan covering
certain independent Trustees of the Fund who will have served as independent
Trustees for at least five years at the time of retirement. Benefits under this
plan are based on factors which include years of service and compensation. The
Trustees voted to close the plan to new participants and eliminate the future
benefits growth due to increases to compensation after July 31, 2003. Aggregate
pension costs for the six months ended December 31, 2005, included in Trustees'
fees and expenses in the Statement of Operations amounted to $3,698. At December
31, 2005, the Fund had an accrued

Active Assets Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2005 (UNAUDITED) continued

pension liability of $63,318 which is included in accrued expenses in the
Statement of Assets and Liabilities.

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.

5. Shares of Beneficial Interest

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

<Table>
<Caption>
FOR THE SIX FOR THE YEAR
MONTHS ENDED ENDED
DECEMBER 31, 2005 JUNE 30, 2005
------------------ --------------
(unaudited)

Shares sold................................................. 2,513,442,477 5,910,005,493
Shares issued in reinvestment of dividends and
distributions............................................. 15,088,143 17,546,368
-------------- --------------
2,528,530,620 5,927,551,861
Shares redeemed............................................. (2,840,557,828) (5,960,568,193)
-------------- --------------
Net decrease in shares outstanding.......................... (312,027,208) (33,016,332)
============== ==============
</Table>

6. Legal Matters

The Investment Adviser, certain affiliates of the Investment Adviser, certain
officers of such affiliates and certain investment companies advised by the
Investment Adviser or its affiliates, including the Fund, are named as
defendants in a consolidated class action. This consolidated action also names
as defendants certain individual Trustees and Directors of the Morgan Stanley
funds. The consolidated amended complaint, filed in the United States District
Court Southern District of New York on April 16, 2004, generally alleges that
defendants, including the Fund, violated their statutory disclosure obligations
and fiduciary duties by failing properly to disclose (i) that the Investment
Adviser and certain affiliates of the Investment Adviser allegedly offered
economic incentives to brokers and others to recommend the funds advised by the
Investment Adviser or its affiliates to investors rather than funds managed by
other companies, and (ii) that the funds advised by the Investment Adviser or
its affiliates, including the Fund, allegedly paid excessive commissions to
brokers in return for their efforts to recommend these funds to investors. The
complaint seeks, among other things, unspecified compensatory damages,
rescissionary damages, fees and costs.

Active Assets Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2005 (UNAUDITED) continued

The defendants have moved to dismiss the action and intend to otherwise
vigorously defend it. On March 9, 2005, Plaintiffs sought leave to supplement
their complaint to assert claims on behalf of other investors. While the Fund
and Adviser believe that each has meritorious defenses, the ultimate outcome of
this matter is not presently determinable at this stage of the litigation, and
no provision has been made in the Fund's financial statements for the effect, if
any, of this matter.

Active Assets 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 SIX FOR THE YEAR ENDED JUNE 30,
MONTHS ENDED -----------------------------------------------
DECEMBER 31, 2005 2005 2004 2003 2002 2001
----------------- ------- ------- ------- ------- -------
(unaudited)

Selected Per Share Data:

Net asset value, beginning of period............ $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00
--------- ------- ------- ------- ------- -------

Net income from investment operations........... 0.015 0.016 0.005 0.009 0.020 0.053

Less dividends from net investment income....... (0.015)+ (0.016)+ (0.005) (0.009)+ (0.020)+ (0.053)
--------- ------- ------- ------- ------- -------

Net asset value, end of period.................. $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00
========= ======= ======= ======= ======= =======

Total Return.................................... 1.56 %(1) 1.61% 0.50% 0.95% 2.01% 5.48%

Ratios to Average Net Assets:
Expenses........................................ 0.59 %(2) 0.58% 0.56% 0.55% 0.53% 0.56%

Net investment income........................... 3.06 %(2) 1.60% 0.49% 0.96% 1.96% 5.24%

Supplemental Data:
Net assets, end of period, in millions.......... $738 $1,050 $1,083 $1,229 $1,427 $1,603
</Table>

- ---------------------

<Table>

+ Includes capital gain distribution of less than $0.001.
(1) Not annualized.
(2) Annualized.
</Table>

See Notes to Financial Statements
14

(This Page Intentionally Left Blank)

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

Charles A. Fiumefreddo
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
Vice President

Francis J. Smith
Treasurer and Chief Financial Officer

Thomas F. Caloia
Vice President

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

The financial statements included herein have been taken from the records of the
Fund without examination by the independent auditors and accordingly they do not
express an opinion thereon.

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.
Morgan Stanley Distributors Inc., member NASD.

[MORGAN STANLEY LOGO]

MORGAN STANLEY FUNDS

Active Assets
Government
Securities Trust

Semiannual Report
December 31, 2005

[MORGAN STANLEY LOGO]

RA06-00113P-Y12/05

Item 2. Code of Ethics.