Boris Johnson has said he is backing David Cameron in response to former media adviser Andy Coulson's claim he wanted to be Prime Minister.
Former Downing Street media adviser Andy Coulson reignited speculation by claiming the London Mayor was desperate to be prime minister but would rather see Mr Cameron "fail miserably" and take his place than stab him in the back.
Boris Johnson said he was backing David Cameron "all the way" and was "increasingly confident" the Prime Minister would win the 2015 election for the Tories, amid fresh claims about his party leadership ambitions.
Responding to the article, Boris Johnson said: "Grateful as I always am to Andy for career advice, I am backing David Cameron all the way."
Andy Coulson, Downing Street's former spin doctor, has compared the relationship between Ed Miliband and shadow chancellor Ed Balls to the "shamefully dysfunctional" Tony Blair and Gordon Brown partnership when Labour were in power.
He wrote in GQ: "The prime minister should pray Ed Balls remains shadow chancellor until the election. Appointing him as George's (Osborne) opposite number was the Miliband gift that will keep on giving...
"The Tories must look for the divisions and make the most of them a) because they are most certainly real - always a plus - and b) because it's history repeating itself. We are in this hole at least in part because of the shamefully dysfunctional Blair/Brown relationship.
"Labour's Two Eds dislike each other and each thinks he is smarter than the other.
"The Conservatives should imagine in some detail how it would work if they actually won...and share that vision with the British public."
On Mr Miliband, he wrote: "The prime minister must push him to take positions: expose his strategy (to keep his head down, silently hope that the economy continues to go wonky and, well, just be the other guy), challenge him to take a view on the tricky issues opposition politicians love to duck.
"I'm struck by how detached the opposition front bench appears to be from their leader... I just don't think they rate him very much.
"And if they don't, there's a good chance the public will feel the same way once they get to know him properly."
London Mayor Boris Johnson "desperately wants to be prime minister", according to Downing Street's former spin doctor Andy Coulson.
Mr Coulson went on: "If proof were needed that our PM is a man untroubled by self doubt, it came in his next sentence - 'so I think he'll be a bloody brilliant candidate for us'.
"Stabbing David, or anyone else for that matter, in the back would be distinctly off brand - just not very Boris. He would much prefer to see David fail miserably in the election and ride in on his bike to save party and country."
London Mayor Boris Johnson is desperate to be prime minister but would rather see David Cameron "fail miserably" at the next election than betray him, former government spin doctor Andy Coulson has said.
Mr Coulson, former No10 director of communications, advised Downing Street to support the mayor's good ideas, "advise privately on the bad ones, but only engage publicly if absolutely necessary - and celebrate Boris's considerable successes".