Boris Johnson is due to address the Conservative party at its annual conference in Birmingham today.
The London Mayor arrived at the event yesterday.
Speaking at a rally, he said Ukip should throw its weight behind the Tories to help defeat Labour.
Boris Johnson took a vital step tonight along his road to a return to Parliament. The Mayor of London has just been chosen as the official conservative candidate in Uxbridge, west of London, for the general election next May .
The London Mayor won on the first ballot and says he is 'obviously thrilled' that the Uxbridge and South Ruislip Conservative Association has chosen him as Tory candidate. He was one of four candidates tonight and faced a series of questions on local issues before his selection was announced just after 10pm.
He has said the next stage will be a 'tough fight' and a 'long fight' and that he plans to remain as Mayor of London until the end of his second term in May 2016.
Labour has criticised Boris Johnson as a "part-time" mayor amid continued speculation that he will return as an MP before the end of his current term.
Renewed speculation in newspapers today suggested that Mr Johnson would announce his intention to stand for parliament at next year's general election by the summer.
A Labour source said the party would attack the mayor if he to "further his own political interests at the expense of the needs of Londoners".
Shadow justice secretary Sadiq Khan tweeted: "Wouldn't it be great if London's part-time mayor cared about our future as much as he cares about his own?"
Former mayor Ken Livingstone added: "Whether Boris Johnson is an MP, in the House of Lords or wherever it will make no difference as he doesn't do the day job as it stands, he leaves it to all his deputies."
London Mayor Boris Johnson has urged larger firms in the capital to pay the London Living Wage of £8.55 to their employees, saying "it doesn't hurt these companies to do a bit more for their employees".
Speaking in a BBC interview after his speech at the Conservative Party Conference, he said there was no reason why large companies should avoid paying the higher rate. "They've got huge dividends, huge profits and it can make a real difference to people on low incomes in London", he said.
David Cameron said he would give London Mayor Boris Johnson "a warm welcome" if he decides to return to Parliament.
The Prime Minister told ITV News' deputy political editor Chris Ship: "I think he's got a huge contribution to make.
"Whenever Boris wants to, he'll get a warm welcome from me".
Boris Johnson reminded Tory conference delegates of his prediction that last year's London Olympics and Paralympics would spur a baby boom.
He told the Conservative Party conference: "I prophesied that the athletes had moved the people of this country to such paroxysms of excitement on the sofas of Britain that they had not only inspired a generation, but probably helped to create one as well."
"Like all my predictions and promises, I have delivered, in that GLA demographics say live births in London will be 136,942, which is more than in any year since 1966 when England won the World Cup."
Mayor of London Boris Johnson has observed that in France they can be both a mayor and Prime Minister at the same time.
A very good idea, he said:
London Mayor Boris Johnson highlighted celebrity chef Jamie Oliver's comments about the work ethic of British young people during his conference speech.
Mr Oliver praised European immigrants in August, saying they are much "tougher" workers than the "wet behind the ears" young Brits.
Mr Johnson asked delegates, "What if he has half a point? Or a quarter of a point?"
He said if that indeed was the case, "don't we need Iain Duncan Smith to get on reforming the welfare system and ensuring you're always better off in work than out of it?"
"And if it's to do with education ... then don't we need Michael Gove to get on with his heroic work of restoring rigour and realism to the classroom?"
Boris Johnson asked the Chancellor George Osborne "to look at the baleful effects of stamp duty" in London and elsewhere during his conference speech.
The Mayor of London told the Conservative Party conference: "It's called stamp duty for a reason, because it's stamping on the fingers of those who are trying to climb the property ladder.
Boris Johnson said the Conservatives have "to recognise that the sheer global charisma of London is putting pressure on Londoners."
Addressing delegates at the Conservative Party conference, the London Mayor highlighted that average house prices are now six times average earnings in the capital.
"The pressure is really growing and it's intensifying," he added.