Cameron may have challenger as Johnson throws hat in the ring

London mayor Boris Johnson has declared his intention to stand for parliament at next year’s general election, putting an end to months of speculation about his ambitions for a return to Westminster.

Prime Minister David Cameron was quick to welcome the announcement, saying he had always wanted to see “my star players on the pitch” during the forthcoming election campaign.

However, Johnson’s declaration immediately raised the prospect that he could emerge as a rival for the Conservative leadership if the party is defeated — or again fails to secure an overall Commons majority — at the polls.

Bookmakers Ladbrokes responded by slashing the odds of Johnson becoming the next Conservative leader from 5/1 to 9/4.

The mayor used a question-and-answer session at the end of a speech in which he highlighted the “attractive” prospects for Britain outside the EU if Cameron fails to secure his promised reforms.

“I think we’ve danced around it an awfully long time now, and as you know the prime minister ages ago said he would welcome me back — very kind of him to say so — and has also been pretty clear that I can’t endlessly go on dodging these questions as I’ve tried to do,” he said.

“So, let me put it this way — I have not got any particular seat lined up but I do think in all probability — since you can’t do these things furtively, I might as well be absolutely clear — in all probability I will try to find somewhere to stand in 2015.”

While he added that it was “highly likely” that he would be unsuccessful in his search for a seat, few at Westminster doubt that his announcement will see him return to the centre stage of British politics.

Cameron, currently holidaying in Portugal, tweeted: “Great news that Boris plans to stand at next year’s general election — I’ve always said I want my star players on the pitch.”

The news will be greeted with mixed feelings in Downing Street. While Johnson’s undoubted popular appeal will be an electoral asset, his return to Westminster will galvanise Eurosceptic Tory MPs determined to secure Britain’s exit from the EU.

Labour’s Sadiq Khan, the shadow minister for London, said Johnson’s announcement showed the Conservatives were turning in on themselves.

“Boris Johnson’s announcement reveals how weak David Cameron is and how out of touch the Tories remain,” he said.

Johnson refused to say whether he had discussed his plans with Cameron, but said it was said it was largely at the prime minister’s instigation that he decided to “have a crack”.

“My conversations with the prime minister are many and various and I don’t propose to go into them,” he said.