Boris Johnson has again failed to dispel rumours he wants to replace David Cameron as prime minister, by echoing the words of another blond Tory who plotted to bring down Margaret Thatcher.

Talking to CNN, the Mayor of London quoted what Michael Heseltine said when he insisted he harboured no ambitions of becoming Conservative leader in 1989 - then tried to oust late prime minister a year later.

Directly citing the Tory grandee with whom he may share more than a mop of blond hair, Johnson told interviewer Christiane Amanpour: "What's it - what did Michael Heseltine say? I want to be mayor of London and I certainly can't foresee any circumstances in which I would be Prime Minister because David Cameron - you look at what's happening now - is steering, I think, ever more comfortably towards a victory in 2015."

It was the latest unconvincing denial by Johnson about how unambitious he is for the top job.

Johnson also said in the interview that his current role at City Hall "gluts the appetite for power".

But choosing to quote the man who is most famous for his bid to win the Tory leadership has raised questions, something Johnson himself almost certainly knew would happen.

Heseltine tried to become leader of the Tories in 1990, as the party reeled from the shock of the hugely unpopular Poll Tax. He went against Thatcher in a contest, but ended up losing to John Major.

A former insider at Number 10 has claimed Johnson is definitely ambitious to get Cameron's job. Former Press chief Andy Coulson, who is facing charges of corruption, claimed the Mayor is hoping the Tories suffer election disaster in 2015.

Former News of the World editor Coulson insisted Johnson is "desperate" to be PM in an article for GQ magazine.

"Boris Johnson desperately wants to be prime minister and David has known that fact longer than most," Coulson wrote.

Speculation about Johnson's ability to depose his former Eton schoolmate peaked during last summer's Olympic Games in London, when a survey revealed Cameron was half as popular as Johnson.

But improving economic figures have buoyed Cameron and boosted belief among Tory MPs in an outright majority at the 2015 elections.

A Labour source told IBTimes UK: "Boris Johnson needs to spend less time grooming himself to be the next Michael Heseltine, and more time getting on with the job he was elected to do.

"Londoners want a full-time Mayor focused on the things that matter - housing, tackling crime and improving transport - not a part-timer only interested in boosting his own political ambitions."