The outgoing head of the Audit Commission has said that ministers used "improper" pressure to interfere with his independent reports on key subjects such as the value of the private finance initiative.

Sir Andrew Foster revealed that the pressure was applied in the run-up to publication of last year's Comprehensive Performance Assessment of local authorities.

In an interview with The Times on Wednesday, Sir Andrew said: "Quite serious pressure was being brought to bear. I certainly took the view that this was improper."

"The situation only resolved itself when I said I would report this and put it into the public domain," he added.

He felt the government was concerned about the prospect of critical reports into PFI deals, which have come under fire for failing to provide the value for money that ministers claim.

As Labour look to provide ambitious improvements in key public services between now and the next election, one unnamed "ministerial aide" was reported to have told today's Independent: "We wish the commission would go away for three years and then assess what we have delivered."

Sir Andrew also alleged that a commission report criticising the value for money of privately financed new schools was delayed because ministers were "unhappy with the message".

Denying the charge of interference in the House of Lords on Wednesday, government minister Lord McIntosh: "It is right that the Audit Commission recommends that we should undertake retrospective evaluation of PFI and indeed we have been doing that and in particular the National Audit Office has been doing that."

He also denied Conservative criticism that PFI deals were being "kept off the balance sheet" for political gain.

"It is simply not the case that the motivation for the Private Finance Initiative is to take anything off the balance sheet. It is no skin off our nose if the proper accounting authorities decide that something should be taken off the balance sheet," he said. "We gain no advantage from it."