Stranger still, on the face of it, is speculation that there could yet be a third casualty of the row: Charlie Wheelan, press secretary to Chancellor Gordon Brown.

The source of the leak about Peter Mandelson's £373,000 loan from former paymaster general Geoffrey Robinson remains as yet unproven.

But suspicious fingers continue to point in the direction of the Treasury and Mr Whelan.

What is certain is that journalist Paul Routledge has been working on a biography of Mr Mandelson - due to be serialised in The Sunday Times in January - which includes a chapter on the home loan.

Mr Routledge has strong links with the chancellor and his closest advisors. His previous biography revealed Mr Brown's prolonged anger at Tony Blair for beating him in the race to become party leader after John Smith's sudden death.

During that time, Peter Mandelson was Tony Blair's right-hand man and Mr Routledge hints of a behind-the-scenes smear campaign being waged against Mr Brown by those backing Mr Blair.

Brown: Rivalry with Mandelson

Mr Mandelson is also said to have initially pledged his support to Mr Brown in the leadership contest, before changing his mind and pitching in with the Blair camp.

Whatever the truth of such allegations, a chasm opened up in the Labour Party between Mr Brown and his team on one side and Mr Mandelson and those close to Mr Blair on the other. This tribalism continued into government.

This had already proved destructive. At the time of the Brown biography, a Downing Street spokesman was widely quoted as saying the chancellor suffered "psychological flaws".

Such unattributed attacks continue. A government minister is quoted in Thusday's newspapers describing Mr Whelan as a "cancer at the heart of government".

The chancellor's press secretary himself denies being the source of the leak, while Deputy Prime Minister John Prescott has pointedly refused to comment on the matter.

The true source of the leak may well be elsewhere. Another certainty in the mire of rumour and suggestion is that Mr Mandelson had no shortage of enemies.

It is also possible, as has been suggested, that the former trade secretary put out the story himself as a pre-emptive strike against the apparent revelations in Mr Routledge's forthcoming book.

One of Mr Mandelson's key advisers, Ben Wegg-Prosser, had apparently received information about the likely content of the biography, which also covers the former minister's sex life.

But the suggestion Mr Mandelson would have done anything to force himself out of the government he professes to love more than anything else on earth was equally denied by those who ought to know.

The full story of who was really responsible for the downfall of the man termed the Prince of Darkness is likely to emerge slowly over the quiet news period of Christmas and the New Year.

Whether Mr Whelan is forced out during that time or not makes little difference to the lasting public impression.

The man who did most to create New Labour has now left the building. And that exit will remain entwinned in the memory with the phrase most often associate with Mr Mandelson and the party he re-built: the spin doctors.