The information requested is available in the Resource Accounts 2006-07 of Cabinet Office: Civil Superannuation, a copy of which is available in the Library for the reference of Members.
Since the 1999-2000 financial year, details of the estimates of the unfunded liabilities of the Principal Civil Service Pension Scheme are published annually in the Cabinet Office: Civil Superannuation Resource Accounts. Copies of these accounts for the years 1999-2000 to 2006-07 are available in the Library for the reference of Members.
Before the introduction of resource accounting in 1999-2000, the accounting arrangements in place did not include pension liabilities and so figures are not readily available. However, for the estimated liabilities at 31 March 1998, I refer the hon. Member to the answer given in the other place by the noble Lord McIntosh to the noble Lord Blackwell on 4 July 2000, House of Lords, Official Report, column WA129.