SOCIAL media went into meltdown yesterday as what has been dubbed #piggate trended worldwide, along with #DavidHameron following lurid claims about David Cameron by billionaire Conservative peer Lord Michael Ashcroft.

The claims came in Ashcroft’s new book Call Me Dave, which is being serialised in the Daily Mail, and which was co-written by Isabel Oakeshott, former political editor of the Sunday Times. Both are Tory publications and Ashcroft is a former Tory Party donor, treasurer and deputy chairman.

He alleged that while at Oxford, Cameron was a member of a “dope smoking group” called the Flam Club; that cocaine was later allowed to circulate in the London home of Cameron and his wife; and that Cameron was part of a debauched Oxford society that specialised in “bizarre rituals and sexual excess”.

A source also claimed that during his initiation ceremony Cameron “put a private part of his anatomy” into a dead pig’s mouth. The source also claimed to have seen photographic evidence.

However, the Prime Minister’s official spokesman dismissed the claims. She said: “I’m not intending to dignify the book with offering a comment. The author has set out his reasons for writing the book. The Prime Minister is focussed on running the country.”

When pressed on specific allegations, she replied: “It’s a line in a book and I’m not going to comment.”

Ashcroft has given millions of pounds to the Tory Party and once had an office next to Cameron’s in Conservative Campaign Headquarters (CCHQ).

He admitted that he had a “personal beef” against the PM, and claimed he and Cameron discussed what role he might undertake if the Tories won the 2010 general election. Ashcroft said a “not insignificant” job was apparently promised.

But there was an outcry over the billionaire’s “non-dom” tax status – which he claimed to have given up 10 years previously. Ashcroft claims in the book that as early as 2009 he spoke with Cameron about how to delay revealing his tax status, which allowed him to avoid tax on overseas earnings, until after the following year’s election.

This contradicts a Tory assertion at the time when the controversial status became known in 2010 that Cameron had been told only a month before.

Cameron did become PM – after the party and Ashcroft were cleared of breaking election rules over the peer’s £5.1 million donations through his company – but only in coalition with the Liberal Democrats.

Cameron later told Ashcroft that his appointment to a senior role had been blocked by his coalition partner, Liberal Democrat leader Nick Clegg. The PM subsequently offered Ashcroft the post of junior whip in the Foreign Office, which he declined.

“After putting my neck on the line for nearly 10 years – both as party treasurer under William Hague and as deputy chairman – and after ploughing some £8m into the party, I regarded this as a declinable offer,” Ashcroft said. “It would have been better had Cameron offered me nothing at all.” However, he added: “Despite my disappointment, my new book about Cameron is not about settling scores.”

However, on the face of it, it would appear that the book is Ashcroft’s revenge, and it surely is being served cold.

For the past five years the 69-year-old has been sitting on the sidelines after relinquishing his non-dom status to keep his seat on the Tory benches in the Lords – a position he has now resigned. But since then he has been constantly critical of Cameron.

Sources close to the Prime Minister said they “did not recognise” the accusations made in the book, which include claims that Cameron was present at events where drugs were taken and was part of a decadent Oxford University dining club.

It was claimed that as a member of the Piers Gaveston society – named after the lover of Edward II – Cameron took part in a bizarre initiation ceremony which involved him inserting “a private part of his anatomy” in the mouth of a dead pig.

Ashcroft said he was told about the incident by an Oxford contemporary of Cameron, who is now an MP and who claimed to have seen a photograph of the event.

The authors said that they tried to contact the owner of the alleged photograph but received no response.

Oakeshott said: “If this was just a revenge job, Lord Ashcroft and I could have published it before the election.”

LibDem leader Tim Farron said the allegations were “extraordinary” but “a bit of a sideshow”.

Valentine Guinness, one of the founders of the Piers Gaveston society, said Cameron was never a member of the group, and the story was “ridiculous”.

He said: “As far as I know David Cameron was never a member of the Piers Gaveston society, so there would have been no need for an initiation ceremony. He may well have attended one of their parties, but the pig’s head story is purely malicious gossip.”

However, the incident was still a worldwide hit on social media last night, and even brought a smile to the face of Chancellor George Osborne, who could barely keep a straight face when asked about it on a visit to China. He said he was not aware of the book.

Cat Boyd: Cameron's unnatural union with a dead pig's mouth tells us much about him

Michael Gray: Piggate is irrelevant, it is real issues that matter

Twitter in meltdown about tale that some say is ‘porkies’

The National View: A penchant for pig? Fine, but it's the other revelations that really damn Cameron