Nick Clegg has said Boris Johnson will have to "come clean" about his steely political ambitions underneath his bumbling persona during what is likely to be a year of feverish speculation about his designs on the Conservative leadership.
The deputy prime minister issued a warning that the London mayor wanted to climb further up the political ladder after Johnson said he would try to return as an MP next year – breaking a "solemn vow" that he would not do so before his mayoral term expired in 2016.
David Cameron has welcomed his former Etonian schoolmate's proposed return to the Commons, saying he needed his star players on the pitch in the run up to the election. But Johnson has repeatedly refused to rule out trying to succeed Cameron as party leader, making him a threat to other potential contenders such as the chancellor, George Osborne, and the homes secretary, Theresa May.
Liberal Democrat leader Clegg, who has been variously branded a "jelly", "condom", "lapdog" and "yellow albatross" by Johnson, suggested the mayor should be clearer about his true intentions.
"I think the thing about Boris Johnson is despite all the clumsiness and bumbliness, he's actually a really, really ambitious politician," Clegg said on his LBC radio phone-in show.
"You don't need to begrudge him that. He treats his political ambition a bit like he treats his hair – he wants everyone to think that he doesn't really care, but he actually really, really does care, and so he'll now have to come clean a bit more about the fact that he is, in many ways, a much more conventional politician than he likes to appear."
Johnson ended years of speculation when he announced his intention to find a parliamentary seat after making a speech on Europe that appeared designed to appeal to the right of the Tory party.
He has supporters who believe his popular appeal could reach non-traditional Tory voters. But his critics are wary of his propensity for gaffes and question whether he pays enough attention to detail.
Johnson is understood to be looking for a London seat and has been hotly tipped to try his luck in Uxbridge, west London.
Announcing his intentions on Wednesday, Johnson said: "It is clear I can't endlessly go on dodging these questions. So, let me put it this way … I haven't got any particular seat lined up but I do think, since you can't do these things furtively, I might as well be absolutely clear, in all probability I will try to find somewhere to stand in 2015. It is highly likely I will be unsuccessful in that venture. You should never underestimate the possibility of things going badly wrong. But I will try that. One thing I must make clear is I will serve out my mandate as mayor of London."
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