Of the mainstream press, only the Daily Mail, which is serialising Lord Ashcroft’s book, has run the allegations on its front page under the headline “Revenge!”

David Cameron once put a “private part of his anatomy” into a dead pig’s mouth during a freakish initiation ritual, it has been claimed.

If an image of the act does exist, selling or distributing it would likely fall foul of the UK’s obscenity laws, which carries a possible prison sentence of up to three years. Cameron has previously refused to comment on similar claims about his activities while at university.

Now, the prime minister’s spokesman will only say that the biographer “himself set out his reasons for writing the book”, refusing to comment further.

Sources close to Mr Cameron last night said they did not “recognise the allegations” in the book, published next month.

Besides fairly prosaic stories of the young Cameron smoking weed and generally being an uber-wealthy Tory numpty, an unnamed source in the book alleges Cameron was a member of a glorified frat boy’s club at Oxford called the Piers Gaveston.

The Daily Mail said that the biography would “make political waves” but the Guardian’s media columnist Roy Greenslade said that “it is highly doubtful that the book will cause more than a ripple”.

While there was apparently no princess involved in this alleged real world story from former Tory treasurer Lord Ashcroft, it’s hard to avoid the obvious similarities.

The Prime Minister later told him Nick Clegg vetoed the appointment, though Lord Ashcroft notes that the former Deputy Prime Minister’s office disputes this.

Lord Ashcroft went on to write a highly-critical report on Cameron’s handling of the 2010 election campaign and eventually retired his parliamentary seat before this year’s general election.

In his account of why he wrote the book, Lord Ashcroft criticises Cameron’s record as Prime Minister, but adds that “my own particular beef with him is more personal”.

Liberal Democrat leader Tim Farron told Sky News the allegations were “extraordinary” but “a bit of a sideshow”.

“It’s not been denied by David, but he’s also said that we are not in the business of saying that politicians can’t have a private life before they come into politics”, Mr Osborne said.