The Government’s spending watchdog is poised to investigate Whitehall’s biggest computer projects after The Times revealed that their costs had overrun by more than £18 billion.

Senior civil servants and company chief executives are expected to be questioned by the National Audit Office (NAO) on why several high-profile computer systems are years behind schedule and have ballooned in cost.

The investigation is likely to focus on eight of the largest Whitehall IT contracts identified yesterday by The Times, spanning the health service, tax collection, benefits, the Armed Forces and the police. Their overall cost to the taxpayer has risen by £18.6 billion from their original estimates.

Edward Leigh, chairman of the Public Accounts Committee, said: “As a result of The Times’s investigation I am going to immediately ask the Comptroller and Auditor-General [the head of the NAO] to investigate the whole matter of government IT spending and in particular the contracts highlighted in the paper.”

The watchdog has the power to demand access to all government documents, including confidential minutes of meetings where big contracts have been discussed. The move comes as a former contractor, who worked with the Ministry of Justice on various computer projects last year, accused the department of waste that “beggared belief”.

Speaking anonymously, the contractor said: “Nothing is co-ordinated. You have about five or six separate companies all being paid millions to do not very much. And then a minister says something in Parliament and the whole project has to be changed.” The contractor said that senior consultants for the department were paid up to £3,000 a day.

The NAO is expected to criticise Ministry of Justice officials severely next month after a prison project overran by £456 million.

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