IT systems have been heavily implicated in a "gargantuan" Whitehall blunder that saw millions of people wrongly advised over partners' rights to their compulsory state pensions after their deaths.
The National Audit Office said taxpayers could face an £8bn bill after the Government postponed plans for two-and-a-half years to halve widows' entitlements under the state earnings related pensions scheme (Serps).
An embarrassed social security minister Alastair Darling announced the delay in the Government's plans to the House of Commons last week.
The chairman of the House of Commons Public Acc-ounts Committee, David Davies, said the affair was "an administrative blunder of gargantuan proportion".
The National Audit Office report said, "the very limited availability of IT within the [Benefit] Agency's local office network, and the archaic nature of much of what exists", contributed to the failure to publicise changes to Serps.
The changes were made in 1986 but only became clear in 1998. Problems were then compounded when the Benefits Agency failed to commission Andersen Consulting, the contractor running the National Insurance Recording System, to make the necessary program changes for the new Serps legislation.