London Mayor Boris Johnson tonight said he did not expect to do "another big job in politics" after leaving City Hall.
Mr Johnson, tipped as a possible successor to Tory leader David Cameron, ruled out standing as an MP while also Mayor - meaning he would be unable to seize the Conservative leadership.
Current rules say the leader must be an MP - and he quashed as "complete nonsense" suggestions he could perform a dual role if he is re-elected as Mayor in May 2012.
He told ITV London Tonight: "Let's take this opportunity to knock this on the head.
"The job of Mayor of London is the most wonderful, most engrossing job I could ever imagine I would have in politics and loads of people realise how lucky I am to be here ... and I really don't want to do anything else. What I want is to get re-elected.
"I've said that I won't go beyond a second term. I'll be well-struck in years."
In an interview for BBC2's Newsnight, Mr Johnson said there was "not a snowball's chance in Hades" he would stand for Parliament while Mayor, adding: "I don't think I will do another big job in politics after this."
Earlier, Mr Johnson delighted activists at the Tory Party conference in Manchester with his vow that London could be the "locomotive" for Britain's economic recovery.
He said: "I give you the wheel deal: you help us to invest in transport infrastructure and we in London will supply the locomotive of the UK economy."
He defended his record since being elected in 2008, saying: "We have effectively cut the council tax by 10% over the last three years, we have put Oyster on the overground, we have delivered a 24-hour freedom pass for the people of London - a fact I hardly dare mention in Manchester in case they get jealous - (and) the last bendy bus will leave our streets by Christmas."
Mr Cameron, who was in the hall for Mr Johnson's address, earlier praised the Mayor, telling LBC 97.3 Radio: "He brings strong, charismatic leadership, he brings people together, he cheers people up.
"The last thing London needs is a return to Red Ken."
But the Labour candidate said: "Today we saw the real Boris Johnson - an out-of-touch Conservative, failing to put ordinary Londoners first on the issues that really affect them, from rising fares to police cuts."
The Liberal Democrats' mayoral candidate, Brian Paddick, said: "Boris's speech was full of waffle because he's done so little for London as Mayor.
"He claims other people's achievements as his own because he doesn't have any himself and he clearly has no vision for the city's future."