Paddick: Clowning Boris is not up to mayor's job

Brian Paddick claimed that Mr Johnson's reported vow to give up drinking for the course of the campaign betrayed a concern that he might commit gaffes.

The former Metropolitan Police commander warned that the would-be Tory mayor would not be able to get through a four-year term of office without embarrassment if he succeeded in ousting Ken Livingstone in May's election.

In an interview with political website ePolitix.com Mr Paddick said: "Boris has got into the habit of believing that nobody will like him unless he makes a joke. There are these accusations of him being racist and him being sexist, but at the end of the day he just can't help cracking jokes and quite often they're offensive to the people that he's making the joke about.

"We need a serious ambassador for London to be our mayor - not a clown."

Mr Paddick said that Mr Johnson's campaign had so far been relatively low-key, apparently because of "some rather fearsome-looking minders" keeping him away from the press to make sure he avoids opportunities for gaffes.

He added: "If the reports are to be believed, he's given up alcohol for the duration of the campaign, presumably for a similar reason. What Londoners have got to realise is four years is a hell of a long time for the mayor to be kept out of the media so he doesn't make any gaffes, and for him to give up drink.

"We're not talking about somebody who can behave for four months of a campaign, we're talking about a mayor who can behave for four years in the interests of London. And quite clearly, Boris can't do it.

"I am quite happy for people to see me after I have had a couple of glasses of wine, but clearly Boris's minders are very concerned that he will revert to type."

Mr Johnson responded by accusing his opponent of talking "pyscho-twaddle".

"Londoners don't want to hear this kind of politically correct psycho-twaddle. I am offering a positive campaign to oust Livingstone, restore security to our streets, buses and station platforms and deliver taxpayer value," he told The Times.

A spokesman for Mr Johnson's campaign told ePolitix.com that although he had decided to give up drinking for the duration it was not a "hard-and-fast" rule.

He said: "Boris wants to be super-fit for the campaign and has already lost a stone-and-a-half in weight.

"The next big drink he plans to have is to help Ken drown his sorrows."