The Department for Transport is today accused by MPs of "stupendous incompetence" over an efficiency drive that was meant to save taxpayers £57m by 2015 but now looks set to cost them an extra £81m.

In one of the most damning reports of recent years, the Commons' influential Public Accounts Committee says the implementation of the DFT's shared corporate services project was "one of the worst cases of project management" it had ever seen.

The department's plan was for the central part of the DFT and its seven agencies to be sharing IT services by April 2008.

Edward Leigh, the committee chairman, explained how the department knew that it was running to a tight timetable but, without a robust challenge to such a risky strategy, ploughed on regardless. "The result," said the Conservative MP, "was lamentable".

He explained how the underlying computer system was inadequately procured and tested, resulting in an unstable set-up when it was switched on.

"DFT staff do not trust the system, which is hardly surprising when we hear that on occasion it took to issuing messages in German," said Mr Leigh.

He added: "So far only the central department and two of its agencies are using it."

"Remember," he stressed, "that this was an efficiency drive aimed at saving £57m by 2015. It now looks like the taxpayer will have to stump up £81m to pay for it."

Mr Leigh added: "The DFT must now work to deliver a functioning system which provides benefits and which its users trust. The department must overhaul its project management capabilities, closely examining the expertise of its project managers."