The government has insisted there is "no truth" to accusations Iain Duncan Smith 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, with secretaries allowed to authorise purchase orders worth more than £20 million.
And The Times reported on Thursday that the work and pensions secretary 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.
The committee's Labour chairman Margaret Hodge said she had not been approached by Duncan Smith, but sidestepped questions about whether she was aware of pressure being put on Conservative colleagues.
She told the BBC: "Iain Duncan Smith didn't approach me. Beyond that I can't comment." Hodge added that the report was agreed unanimously and "from the top down everybody is responsible for the mess that we have seen in the administration and evolution of this programme".
A spokeswoman for 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."
Speaking in the Commons on Thursday, the leader of the House Andrew Lansley rejected repeated calls from Labour MPs for Duncan Smith to be summoned to the chamber to answer the allegations.
"There is no need for a statement. There is no truth in the allegations made about talking to members of the public accounts committee." he said. "The allegations are not true. I have had conversation with the secretary of state and there is no truth in the allegations."
"I have no reason to believe the independence of the public accounts committee has been compromised in any way."
Conservative backbencher Stewart Jackson, who sits on the public accounts committee, also told MPs that "no pressure was exerted" on PAC members.
In its strongly-worded report, the PAC voiced doubts about whether Universal Credit can still be fully delivered by 2017 - branding a pilot "inadequate" and open to fraud.
Hodge said the implementation of Universal Credit so far had been "extraordinarily poor". She added: "The failure to develop a comprehensive plan has led to extensive delay and the waste of a yet to be determined amount of public money."
"From the outset, the Department has failed to grasp the nature and enormity of the task, failed to monitor and challenge progress regularly and, when problems arose, failed to intervene promptly. Lack of day-to-day control meant early warning signs were missed, with senior managers becoming aware of problems only through ad hoc reviews."
A DWP spokeswoman said: "Universal Credit (UC) is a vital reform that rewards work instead of trapping people on benefits. It will ultimately bring a £38 billion economic benefit to society.
"This report doesn't take into account our new leadership team, or our progress on delivery. We have already taken comprehensive action including strengthening governance, supplier management and financial controls.
"Since we have last spoken to the PAC, we have also launched Universal Credit in Hammersmith, which will expand to further areas later this month and the claimant commitment is rolling out to Jobcentres across the country.
"We don't recognise the write-off figure quoted by the committee and expect this to be substantially less. The head of Universal Credit, Howard Shiplee, has been clear that there is real potential to use much of the existing IT. We will announce our plans for the next phase of UC delivery shortly."