White Mountains Insurance (WTM) 10-Q 2006 Q1 Quarterly report

Exhibit 32.2

PRINCIPAL FINANCIAL OFFICER

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of White Mountains Insurance Group, Ltd. (the “Company”) on Form 10-Q for the period ending March 31, 2006 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, David T. Foy, Executive Vice President and Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:

•The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and,

•The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of and for the periods presented in the Report.

/s/ David T. Foy

Executive Vice President and Chief Financial Officer

(Principal Financial Officer)

Date: April 26, 2006