Cabinet minister Iain Duncan Smith has dismissed claims he attempted to pin the blame for "shocking" failures in his flagship welfare reform on his senior official.
A scathing cross-party report on the Universal Credit scheme found that at least £140 million has already been wasted on the project, which was blighted by "alarmingly weak" management.
It said secretaries had been allowed to authorise purchase orders worth more than £20 million. In some cases, it is unclear what suppliers have been paid for.
The Times reported that Work and Pensions Secretary Mr Duncan Smith and members of his parliamentary team approached Tory members of the Public Accounts Committee (PAC) to ensure that the department's chief civil servant Robert Devereux was singled out for criticism.
But a spokeswoman for Mr Duncan Smith said: "Iain has not asked for anyone to be named in the report. He has publicly supported the Department for Work and Pensions permanent secretary throughout this whole process."
The committee's Labour chairman Margaret Hodge said she had not been approached by Mr Duncan Smith, but sidestepped questions about whether she was aware of pressure being put on Conservative colleagues.
David Cameron's official spokesman was also evasive on repeated questions from reporters about whether the Prime Minister was "confident" that Universal Credit would be delivered on time and on budget.
He said: "The department is working to the 2017 timetable. That is the timetable that the department continues to work to."
Pressed on whether it was right for ministers, rather than senior officials, to take responsibility for failings in implementing major policies, the No 10 spokesman said the Prime Minister had previously insisted that "everyone has to take their responsibility."