Labour must win Mayor of London election to prove Jeremy Corbyn's appeal, warns Tristram Hunt

Mr Hunt gives Labour leader seven months to demonstrate he can reach floating voters MP who refused to serve under Mr Corbyn says he 'would expect' party to do well in London

Sadiq Khan has been selected as the Labour candidate to contest the mayoral election, and is currently regarded as the narrow favourite to succeed Boris Johnson (Rex)

The Labour Party needs to win next year’s Mayor of London election to prove that Jeremy Corbyn can reach out to floating voters, a leading centrist MP has warned at the party conference.

Tristram Hunt, who refused to serve under the new leader, effectively gave Mr Corbyn just over seven months to demonstrate his appeal to the electorate. The shadow Chancellor, John McDonnell, won cheers from activists in Brighton as he urged people who had stood down from the Labour frontbench to “come back and help us succeed”.

Mr Corbyn’s internal critics are biding their time in recognition of the convincing mandate he won from party activists in the leadership election. But Mr Hunt set the clock ticking by saying the new leadership team had to “deliver successfully” in the London mayoral, Scottish, Welsh and local council elections next May.

London is a Labour city... So quite rightly there is expectation on the leadership to deliver, and deliver successfully, next May

&#13; <p>Tristram Hunt</p>&#13;

“I would expect us to do well in those elections. It will be us heading towards mid-term territory, a government that has been in power for six years,” he told a fringe meeting hosted by The Times.

“There will be discontent. London is a Labour city... So quite rightly there is expectation on the leadership to deliver, and deliver successfully, next May.”

Sadiq Khan has been selected as the candidate to contest the mayoral election, with Zac Goldsmith expected to stand for the Conservatives. Mr Khan is regarded as the narrow favourite to succeed Boris Johnson because of growing Labour support in London over the last decade.

Mr Hunt said he was a “big supporter of what Jeremy Corbyn wants to do in terms of an open debate”, but said that he should face up to the “hard truths” about the reasons for Labour’s heavy defeat in May’s general election.

Dan Jarvis, who has been touted as a future Labour leader, also said that the 2016 local elections, or any parliamentary by-elections which arose, provided the party’s next big test. Speaking at a Huffington Post fringe event, he argued that politics was about winning the “opportunity to change the country for the better”.

He said that Labour must now build a platform “grounded in the reality of the lives people lead”, addressing public concern on such issues as the economy, immigration and welfare.

“We have got to bring forward a policy agenda to the public that they think is credible and that they can vote for,” he said.

Mr Jarvis also hinted at their policy differences, stressing the importance of stating unequivocally Labour’s support for membership of Nato and the European Union.

The former Army officer also put himself at odds with his leader by arguing that it would be prudent to wait for the Chilcot report into the Iraq war before apologising for Britain’s involvement in the invasion.

And asked about Mr McDonnell’s comments a decade ago calling for the IRA to be “honoured”, Mr Jarvis said: “It is clearly not something I am personally comfortable with at all.”