The suggestion that the civil service could be cut by up to 90% is not the policy of the prime minister or "anyone else in Number 10", the cabinet secretary has insisted.
In what could be interpreted as a final swipe at David Cameron's director of strategy Steve Hilton, who left Downing Street for California last week, Sir Jeremy Heywood said leaks to the press that suggested as much had "no authority whatsoever".
In the days leading up to Hilton's departure stories appeared in the papers detailing proposals included in his final memo - claiming the government could make radical cuts to the Whitehall machine and slash a further £25bn from welfare.
Hilton has taken a year-long sabbatical from government, and there continues to be intense speculation as to whether he'll come back.
There are currently 434,000 civil servants in Whitehall, and Hilton is said to have suggested a trial run of slashing one department by 70% before cutting the total number of officials by 90%.
Sir Jeremy told the Commons public administration committee on Thursday that this plan did not "remotely reflect the view" of the government and that Cameron and Clegg "totally share" his anger at the reports.
"They are just as frustrated and angry as myself and Bob Kerslake [the head of the civil service] when that is put in the papers," he said.
He added: "There has clearly been briefings in the newspapers."
Asked where he thought the leaks came from he said: "I don't know whether it's definitely come from Steve Hilton."
He earlier observed: "The way Steve operates is to challenge, he is a very challenging person."
Lib Dem chief secretary to the Treasury Danny Alexander alluded to the incident at a recent lunch for journalists, when he noted most people did not make such controversial proposals when leaving a job. "On their last day, they usually bring in a cake," he said.
There have been widespread reports of tension between ministers and senior civil servants in recent months. The perception that mandarins were blocking radical reforms desired by Hilton is said to have persuaded him to quit government.
Acknowledging the tension Sir Jeremy said: "It is true some ministers and advisers have been frustrated. I know in some quarters there is frustration at the pace of change."
Sir Jeremy also insisted he had not been upset by the prime minister's past attack on the civil service as the "enemies of enterprise".
The cabinet secretary said he thought those words had just been a "rhetorical flourish" although he admitted his colleagues were "a little surprised by it".