LONDON -- British Prime Minister David Cameron's university days at Oxford are in the news thanks to a new book by a former Conservative Party treasurer.

Michael Ashcroft, who donated millions to the party before falling out with Cameron, has co-written "Call Me Dave," an unauthorized biography that includes allegations of undergraduate drug-taking and juvenile sexual escapades.

Extracts published Monday in the Daily Mail newspaper claim Cameron smoked marijuana with friends -- often while listening to 1970s rock group Supertramp. The book also quotes an unnamed college contemporary as saying Cameron once inserted "a private part of his anatomy" into the mouth of a dead pig during an initiation ritual for a student club.

Downing Street said Cameron would not "dignify" the claims with a response, and they are likely to prove more embarrassing than harmful. Satirical responses flourished on social media under the hashtags #piggate and #hameron.

Cameron, 48, has often sought to play down his privileged upbringing. He attended Eton College, the country's most famous private school, and Oxford, where he was a member of the Bullingdon Club, a raucous drinking-and-dining society with a reputation for drunken vandalism.

Downing Street portrayed the book as political revenge by an aggrieved former colleague.

Ashcroft, who co-authored the book with journalist Isabel Oakeshott, wrote that he had a "beef" with Cameron because he was not offered a senior government job as promised after the Conservatives were elected in 2010.

His most potentially damaging allegation is a claim that Cameron knew in 2009 that Belize-based Ashcroft was registered as "non-domiciled" in Britain and did not pay U.K. tax on his foreign earnings.

Ashcroft's tax status embarrassed the Conservatives when it was revealed in 2010, but Cameron claimed he had not previously been aware of it.