Differences between David Cameron and a major Conservative donor have burst into the open with the serialisation of a book containing allegations about the Prime Minister's time as a student.
The allegations are in a book entitled Call Me Dave by billionaire peer Lord Ashcroft and journalist Isabel Oakeshott, serialised in the Daily Mail.
Downing Street has declined to comment on its contents, which are likely to cast a shadow over the Conservatives' upcoming annual conference in Manchester.
Sources close to Mr Cameron said they "did not recognise" the accusations, which include claims that Mr Cameron was part of a decadent Oxford University dining society and was present at events where drugs were taken.
In the book, due to be published next month, Lord Ashcroft says he has a personal "beef" with the Prime Minister after his failure to offer him a significant job in his administration following the formation of the coalition government in 2010.
He claimed the PM initially blamed Liberal Democrat coalition partners for blocking his appointment, before offering him a junior role at the Foreign Office which the peer described as "declinable", adding: "It would have been better had Cameron offered me nothing at all."
Ennobled by William Hague in 2000 after saving the party financially as treasurer in the wake of its disastrous 1997 election defeat, Lord Ashcroft has given around £8 million to the Tories and was deputy chairman during Mr Cameron's period as leader in opposition.
In his book, Lord Ashcroft claims that as early as 2009 he spoke with Mr Cameron about how to delay revealing his "non-dom" tax status until after the following year's election.
This contradicts a Conservative assertion at the time when the controversial status became known in 2010 that Mr Cameron had been told only a month before.
Lord Ashcroft later gave up his non-dom position, which allowed him to avoid tax on overseas earnings, in order to retain his place on the Conservative benches in the Lords.
He wrote a highly-critical report on Mr Cameron's handling of the 2010 election campaign and eventually retired his parliamentary seat ahead of this year's general election.
He has remained highly active in the political world as an opinion pollster and commentator.