Mr Whelan said he would leave his post at the Treasury on Monday following speculation he was behind the revelation that former trade secretary Peter Mandelson borrowed �373,000 from millionaire MP Geoffrey Robinson.

Mr Whelan has denied that he was the source of the leak, which resulted in the resignation of both Mr Mandelson and former paymaster general Mr Robinson.

Michael Ancram: "Resignation raises more questions"

Conservative Chairman Michael Ancram said the government "was coming apart at the seams" and Mr Whelan's resignation raised even more questions.

He told BBC Radio 4's The World At One programme: "Was he authorised by Gordon Brown?

"If he was authorised by Gordon Brown, is he as culpable as Charlie Whelan is?"

Shadow Chief Secretary to the Treasury David Heathcoat-Amory said: "This is another typical Labour resignation: 'I'm innocent, but I'm resigning'.

"But nothing can conceal the fact that this is an admission that Charlie Whelan was behind the story that led to Peter Mandelson's resignation.

Charlie Whelan: Denied leaking loan details

"If Charlie Whelan has to go, he should go now. He has access to sensitive information and he is paid more than �50,000 a year by the taxpayer. He should not be allowed to hang around until he gets another job."

Mr Heathcoat-Amory went on: "The real problem is not one out-of-control spin doctor.

"The real problem is ministers who are so obsessed with their own fiefdoms and doing down their colleagues that the business of government - and the interests of Britain - are suffering."

Mr Heathcoat-Amory said Mr Whelan's imminent departure raised questions about Gordon Brown's position.

Malcolm Bruce: "Slow death won't help bosses"

Liberal Democrat Treasury spokesman Malcolm Bruce welcomed Mr Whelan's resignation.

He said: "He should leave his post immediately, as he can no longer speak for the government with any credibility - the period of slow death will help neither Mr Whelan or his Labour bosses."

Mr Bruce said the chancellor's position had been "seriously weakened" after losing Mr Whelan and, last month, Geoffrey Robinson as paymaster general.

Former lobbyist Derek Draper told The World At One Mr Whelan's position had become untenable even if he had not had any involvement in the leak.

Derek Draper: Mr Whelan's position was 'untenable'

He said: "His crime was to antagonise so many members of the Cabinet.

"I think that Charlie Whelan's position was becoming untenable even if he was as innocent as his friends claim, which I doubt, it had got to the stage where he was more a liability than an asset to Gordon Brown and inevitably he was going to go."

Labour backbencher Brian Sedgemore, a member of the Treasury Select Committee, said he was "very sorry" to see Mr Whelan go.

He said: "I have always thought he was a splendid press officer and a good colleague and a very sociable person to be with.

"He's done a first-class job for Gordon Brown and Gordon has done a first-class job.