What does David Cameron really think of Lord Ashcroft?

For more than 24 hours now, Downing Street has been refusing to dignify Lord Ashcroft's allegations with an official response.

Privately Downing Street officials have been dismissing the claims contained in the peer's biography of David Cameron as "ridiculous" and "nonsense".

But what does the prime minister think himself about the lurid allegations of drug taking and porcine ritual?

Well, he gave some sense of his views at a Conservative fundraising dinner at the Carlton Club last night.

He told the 300 guests that he had had to go to hospital earlier in the day for a bad back, the result of some over-energetic wood chopping in his constituency at the weekend.

The surgeon told Mr Cameron that he would need an injection and asked him to lie on his front.

The doctor then said: "This will just be a little prick, just a stab in the back."

Which, the prime minister said, "rather summed up my day".