Jeremy Corbyn says he could work with Andy Burnham as Labour leader

Jeremy Corbyn is the surprise front-runner in the Labour leadership contest

Jeremy Corbyn has said he could work with Andy Burnham should the latter win the Labour leadership contest.

Mr Burnham had earlier said that if he won he would offer Mr Corbyn a role.

But fellow leadership candidate Yvette Cooper said Mr Burnham should withdraw from the race if he was not prepared to oppose the left-winger.

And ex-party leader Neil Kinnock said Labour supporters must choose between "seriously" contesting elections and being in "perpetual demonstration".

Lord Kinnock did not directly name Mr Corbyn, the front-runner in the contest according to polls, but criticised those in the party he said were resorting to "corrosive self-indulgence".

Speaking to BBC Two's Newsnight, he said that being a party of demonstration was "fulfilling and noble, but rarely effective".

He added: "I can see why people are angry and want to protest. But then they've got to make a decision on whether they want to be part of a Labour movement that produced a political party to seriously contest for democratic power - or they want to be in perpetual demonstration."

Everything you need to know about the four candidates hoping to become the next Labour leader

Also on Newsnight, Mr Corbyn responded to Mr Burnham's conciliatory comments by saying: "Obviously there has to be a party of all the talents and of course, we can work together, and that's an easy thing to do."

But Mr Burnham's comments prompted criticism from fellow leadership rival Yvette Cooper.

Her spokesman said: "If he [Mr Burnham] isn't prepared to offer an alternative to Jeremy, he needs to step back and leave it to Yvette.

"And he should do the right thing by the party and tell people who do still support him to put second preferences for Yvette - something he is still refusing to do."

Mr Burnham's campaign chief Michael Dugher told The Guardian: "It's time now to rally behind the only person in this contest who can beat Jeremy Corbyn and that is very clearly Andy Burnham."

Labour leadership contest

Leadership contenders: Liz Kendall, Andy Burnham, Yvette Cooper and Jeremy Corbyn

• Who are the candidates? Andy Burnham, Yvette Cooper, Jeremy Corbyn, Liz Kendall

• Dates: Ballot papers were sent out on 14 August; voting can take place by post or online. They must be returned by 10 September. The result is announced on 12 September

• Who can vote? All party members, registered supporters and affiliated supporters - including those joining via a union. More than 160,000 people signed up to vote as supporters, full members or union affiliates in the final days before the registration deadline, bringing the total size of the electorate to 610,000

• What is the voting system? The Alternative Vote system is being used, with voters asked to rank candidates in order of preference

• How does it work? If no candidate wins outright with more than 50% of first preferences, whoever is in fourth place drops out and the second preferences of their backers are reallocated to the other candidates. If there is still no winner the third placed candidate is then eliminated with their second preferences similarly reallocated. The candidate who has accumulated the most votes through the different rounds then wins.

Former Foreign Secretary David Miliband has declared he is backing the fourth contestant in the leadership race, Liz Kendall.

Ms Cooper and Ms Kendall have both said they would not serve in a Jeremy Corbyn shadow cabinet, arguing that policies such as renationalising utilities and scrapping Trident were not credible.

But Mr Burnham has tried to strike a more consensual tone, amid speculation he is going after the veteran Mr Corbyn's second preference votes.

Mr Corbyn said he welcomed Mr Burnham's "inclusive tone".