The election campaign for London’s mayor descended into personal abuse yesterday as Boris Johnson, the Tory candidate, was dismissed as a “clown” by his Liberal Democrat rival.

Brian Paddick, the former Metropolitan Police commander, who is standing for the Lib Dems, claimed that Mr Johnson would be unable to represent the city without embarrassing and offending Londoners.

He accused Mr Johnson, who has faced criticism over claims that his campaign has been too low-profile, of being shackled by Tory party “minders” given the task of keeping him out of trouble until the election in May.

Mr Johnson’s camp responded with an attack on the Lib Dem candidate for negative campaigning. One ally of Mr Johnson said: “People want to hear from candidates about what they are going to do about policing, transport, housing, the Olympics. They don’t want to hear bitching between candidates.”

The spat follows other attacks during the campaign in which allies of Ken Livingstone have tried to brand Mr Johnson a racist, and the mayor has complained of a smear campaign against one of his associates.

Mr Paddick triggered the row in an interview for the website ePolitix.com in which he claimed that Mr Johnson’s public appeal was based on making jokes at the expense of other people. He 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.

“And we need a serious ambassador for London to be our mayor - not a clown.”

Mr Paddick also questioned the decision by his Tory rival to give up alcohol until polling day, suggesting that he had done so at the behest of Conservative party “minders” to avoid making blunders during the campaign.

“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,” Mr Paddick said.

“We’re not talking about somebody who can behave appropriately 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.

“Clearly, Boris is under strict orders not to be himself and clearly once you have had a drink or two you tend to become more yourself than if you haven’t had a drink, you let your defences come down and the true you comes out.

“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 after he’s had a couple of glasses of whatever his particular tipple is.”

Mr Johnson’s camp insisted that the decision to give up drinking until polling day had been his own because during the campaign his day routinely began at 6.30am and often ended at midnight.

Mr Johnson responded to the attack by accusing his Liberal Democrat opponent of talking “psycho-twaddle” rather than focusing on issues that mattered to voters.

He told The Times: “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.”

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