David Cameron made an unscripted dig at Lord Ashcroft during his speech at Conservative Party Conference.
He told delegates in Manchester: "That was a great speech yesterday Boris, a fabulous speech.
"I was a hooker. And by the way that’s a factual statement, not a chapter in Ashcroft’s new book," he added.
Lord Ashcroft made a number of allegations in his unauthorised biography Call Me Dave, but the one which caused the most furore alleged that the Prime Minister had once inserted his genitals into a dead pig's mouth while studying at Oxford University.
The claim was discussed on social media using the hashtag #piggate.
A spokesperson for the Prime Minister previously told The Independent: "It’s a no comment from us. On any of it."
After the joke, Mr Cameron turned to the matter of tackling "entrenched social problems" and the "long-term economic plan".
