A former News of the World political editor has said Lord Ashcroft's story about David Cameron and a pig's head would not have made it into his former newspaper.

The claim, part of Ashcroft's biography of the Prime Minister, features on the front page of the Daily Mail today.

Writing in The Spectator today, Ian Kirby said: "If I had gone to Rebekah Brooks or Andy Coulson when they were editing and said that I had a story about David Cameron’s honourable member and a pig’s head, their first question would be ‘where’s the proof?’"

"If I then told them I had it on good authority from an MP who swears they’d seen a photograph but won’t go on the record, I would have been booted out of the office – only after being given a good kicking.

"As every political journalist knows there are lies, damn lies – and then the tales that MPs tell about their enemies. Lord Ashcroft’s story about Cameron and the pig would not have passed the basic standards demanded by a tabloid newspaper."

Kirby also wrote that tabloids do not have the budgets they used to have and so the "easy way for a newspaper to publish a scandal nowadays is simply to serialise a book, preferably one by a ‘name’, and then print whatever they say about someone you know doesn’t have the time or the inclination to sue. It’s not the paper’s reputation on the line but the author’s."

He added: "Politicians like to attack the press for low standards, sometimes for good reason. But today we see a revolting ‘story’ that is based on nothing more substantive than the ‘word’ of a multi-millionaire."