Boris Johnson has admitted "fudging" whether he will return as an MP at the 2015 election.
The London mayor's comment came after David Cameron said he would welcome his return to the Commons.
But it will not be in the seat of Richmond, after Tory MP Zac Goldsmith told HuffPost UK the mayor would not be able to "trampoline" back to Westminster using his constituency.
Cameron told BBC Radio 4's Today programme that the mayor could "absolutely" make a comeback before the country goes to the polls in 17 months' time, and said he would give him a "warm welcome".
Johnson was mobbed by media and Tory activists as he toured the exhibition hall at the party's conference in Manchester.
During a round of broadcast interviews, he was asked by BBC Radio 5 Live whether he was determined to keep fudging his answers on whether he wanted to return as an MP in 2015.
"Yes," he replied to laughter.
Johnson, who served as member for Henley until 2008, dodged a barrage of questions about the possibility of serving as mayor and an MP at the same time.
Stressing his commitment to his current role - to which he was re-elected last year - Mr Johnson said: "I have got a huge job to do... I am going to give it my all.
"I don't want to leave office until some of the things we have got going are absolutely in the bag.
"The programme is to be mayor of London for the next 750 days, or whatever it is."
Asked which parliamentary seats he could look at if he did seek a return, Mr Johnson said: "The seat I want, I can describe it to you, it has a spongey bottom bit and it swivels and it is to be discovered in the office at City Hall."
The mayor said Mr Cameron's words about him were "very kind", but insisted the Tory leader was capable of winning the general election without his help.
"I am a toenail in the body politic," he joked.
Goldsmith said there were MPs who would be prepared to give up their seats to allow Johnson to return to Parliament so he could "advance his ambitions to become prime minister".
But the MP - who was at one time reported to have offered to vacate his seat to make way for Mr Johnson's return - said it would not be him.
"In terms of Boris using Richmond as a trampoline to Parliament to advance his ambitions to become the prime minister, he may well have his ambitions, but he's not going to do it from Richmond," he told a Huffington Post UK fringe meeting at the Conservative Party conference in Manchester.
"It's a very complicated seat, it's very volatile, it's very demanding. I don't think you'd survive two minutes if you took your eye off Richmond and focused everything on Parliament. I think he knows that."