Ed Miliband's speech arguing that he should be judged on his ideas rather than his "not from central casting" image was a "watery and flavourless consommé of nothingness", according to Boris Johnson.
The Mayor of London explained in the Daily Telegraph that he had forensically analysed the Labour Party leader's anti-photo opportunity and anti-media gimmick "The Choice" speech, but failed to discover any "new or big" ideas.
"I have sieved it and strained it for the smallest crouton of substance, anything at all that you could get your teeth into," the Conservative Party politician said.
"It is not a rich minestrone of policies. It is a watery and flavourless consommé of nothingness.
"There is absolutely nothing that corresponds to an idea that is either new or big; just a couple of paragraphs in which he makes a passing allusion to some of his small, old, bad ideas."
The comments comes after Miliband, who was criticised earlier this year for posing with a copy of The Sun newspaper, pledged that the British public would have their own version of Prime Minister's Questions if Labour comes to power after the 2015 General Election.
"I think what we need is a public question time, where regularly the prime minister submits himself or herself to questioning from members of the public in the Palace of Westminster on Wednesdays," Miliband told the BBC.
"At the moment there is the glass that separates the public in the gallery from the House of Commons, but there is a gulf miles wide between the kind of politics people want and what Prime Minister's Questions offers."
Miliband will submit proposals to the Commons Speaker John Bercow on the issue.