Boris Johnson has suggested he will stay out of the Cabinet while he remains London Mayor, but has left the door open to taking a job as minister without portfolio.
The Conservative candidate for Uxbridge and South Ruislip reaffirmed his plans to remain in the capital’s top job until his term ends in 2016 if he is elected in the safe seat at the general election.
Pressed about the role he will play if the Tories win in May, he did not rule out taking on a roving role.
In an interview with the Evening Standard, Mr Johnson said it would be “totally deranged” to quit as mayor.
“Why would I want to do that? That would be insane, totally deranged, it is the most wonderful job,” he said.
Mr Johnson said it was possible to combine the job of an MP with another large role, pointing to the positions of prime minister and chancellor, who have the “whole country to run”, but said being mayor was not compatible with running a government department.
Asked about the possibility of him becoming minister without portfolio, he told the paper: “All of this is entirely fruitless, bootless, useless speculation. I’m going to get on with delivering my mandate as mayor.”
He added: “I will continue to speak as I find and say what I want - that’s what a politician should do. Of course I will.
“By the way, one of the questions that people can reasonably ask is will I continue to speak up for London? The answer is yes. Whatever happens to me politically I absolutely guarantee. I have learnt a huge amount over the last six or seven years, insofar as it is possible for people to change, I think I’ve changed.”
Mr Johnson is returning to New York for talks with his counterpart in the city as he completes his US trade mission.
Bill de Blasio pulled out of a meeting with the mayor earlier this week citing ill health - despite attending an event at New York University.same evening.
The left-wing New York mayor is expected to be well enough after recovering from a cold to discuss ways of boosting links between the two cities at the rescheduled talks this evening.
After arriving back in city, Mr Johnson will head straight to the 9/11 memorial and then take a tour of the New York Fire Department.
It comes after a fleeting visit to Washington DC that has seen Mr Johnson, who is regularly tipped to succeed Prime Minister David Cameron as Conservative leader, bolster his contacts in the capital.
He attracted a strong turnout at a 40-minute lunch on Capitol Hill with senior House of Representatives and Senate Republicans and Democrats, which followed a 20-minute one-to-one meeting with House majority leader Kevin McCarthy.
The discussion ranged across key international issues, including strong support for sticking to the Nato target of spending 2% of national income on defence, or even exceeding it, and the latest developments in the fight against Islamic State (IS).
During a question-and-answer session at the Brookings Institution, Mr Johnson called on Chancellor George Osborne to hand massive financial powers to cities to help “detoxify” British politics.
Westminster was going through a “very rocky period” and devolution would help to “electrify the political scene”, he said.
Mr Johnson said devolving fiscal powers would give cities a mandate to push growth policies instead of having to go “begging for penny packets of funding”.
He said: “To get it done you simply have to get the Treasury to understand that they make more money out of this. They have nothing to fear.
“Even a Labour mayor couldn’t possibly make a hash of this.”
Mr Johnson insisted he had not been weighing up his chances of succeeding David Cameron as Conservative leader following the May 7 general election.
“I haven’t thought about it,” he told LBC radio, adding: “Ultimately one day in the dim distant future when David Cameron relinquishes the Premiership back to, some babe unborn will take over but I think that ... the vacancy is unlikely to arise for the foreseeable future.”
Asked whether he would save Mr Cameron or George Osborne if he found himself in a lifeboat with only room for one of them to join him on board, Mr Johnson said: “I immediately plunge, dive overboard, and offer them the dinghy in the knowledge that I can swim heroically to land myself. That’s what I’d do.”
The Mayor said he would be “very sad” when his term ends in 2016, adding: “This has been unquestionably the happiest and most productive part of my professional life and it has been an unbelievable privilege to work for London.”
But he rejected suggestions he should fight again for a further four years at City Hall, and suggested that Margaret Thatcher and Tony Blair outstayed their welcome by remaining in office into a third term.
“You need fresh challenges as a politician and you need to be thinking about how you can do things differently and I think it’s a mistake to outstay your welcome,” said Mr Johson.
“I’ve loved the job and you think about Blair and Thatcher and all these people who hang on and hang on and hang on, it all ends in... All political careers end in tears in one way or another, of course, quite rightly - it would be totally wrong if it didn’t. Wretched politicians, they need to be kicked out.
“But the job of Mayor I always thought was two terms max and obviously I’m looking forward, if I can, to getting back into Parliament in May.”
Mr Johnson said that the UK was regarded as “the bright spark” of Europe by Americans, and rejected suggestions that Britain’s leaders should shift their focus away from an economically declining USA to concentrate on the emerging giants of the East, like China.
The Mayor told LBC radio: “We are doing unbelievably well in American eyes. They think we’re the best, the bright spark, by far the best bit in the whole European economy, a place of real zap.
“I think that they feel that London is the kind of America of the European Union. It’s the place where they want to come, it’s the place where they recognise an enterprise culture and we’re very lucky in that respect.”
Predecessor Ken Livingstone has argued that the Mayor should be touring eastern countries, rather than the US. But Mr Johnson said: “This is the strongest economy in the world still - and, by the way, I think America will continue to dominate the world economically for as long as we’re alive, culturally and politically as well.
“I think America’s decline has been wildly exaggerated. This is overwhelmingly the biggest source of investment in London. This is the overwhelmingly our single biggest export market and there’s more to do. So of course Ken’s right in the sense you’ve got to go for the growth markets and we’ve been doing that, but you’ve also got to capitalise on where you’re strong.”