PRWeek also understands that the Number 10 press office is highly unlikely to change that tactic in the coming days in relation to the biography, which is being serialised in the Daily Mail.
Other national newspapers have also picked up on the book's content, whose most eye-catching detail is that the PM once "put a private part of his anatomy" in a dead pig's mouth as part of an initiation ceremony for a private society while at the University of Oxford.
The #piggate hashtag was still trending on Twitter at the time of writing, with many social media users mocking the Prime Minister. More than 310,000 tweets have been created using the hashtag, and a specially edited Cassetteboy video entitled 'Getting Piggy With It' has received over 850,000 views.
Isabel Oakeshott, the journalist who co-wrote the book with Lord Ashcroft, defended the publication of the story in a radio interview with LBC's Nick Ferrari.
"It's a small anecdote about student high jinks. The story came to me over dinner. Initially I thought it was a joke," she said.
Oakeshott went on to say: "The story came from a very respected MP, I won't be saying any more about who it was."
"The bottom line is: we could not be sure whether he was telling the truth or not. We weren't able to find dozens of people who were witnesses and so we reported it just as that. It was an account that was given to us by a respected MP and people can make up their own minds - maybe he did it, maybe he didn't."
Ashcroft’s book also alleges that the Prime Minister was a member of a "dope-smoking group" called the Flam Club at Oxford, that he was part of an Oxford society that specialises in "bizarre rituals and sexual excess", and that cocaine was allowed to circulate in he and his wife’s London home.
In addition to this, Lord Ashcroft also claims that David Cameron knew about the peer’s 'non-dom' tax status as far back as 2009 - despite Cameron claiming that he did not know about this until 2010.