Gordon Brown’s chances of facing a left-wing leadership challenge rose last night after it emerged that his two declared challengers are pooling resources to try to gain enough support to enter the contest.

John McDonnell, a backbencher, and Michael Meacher, a former Environment Minister, are preparing to announce a deal that would mean that the candidate with less support drops out, backing the other.

Challengers for the Labour leadership must secure the support of 44 MPs to get on the ballot paper. But last night The Times discovered there are tensions between the two candidates, with Mr McDonnell saying that a deal had been struck but Mr Meacher saying the details still had to be worked out.

Mr McDonnell said: “For the last three months we have been trying to get Michael Meacher to sit down and say that whoever has the highest number of MPs goes forward. Yesterday we sat him down and he agreed to that. But we’ve been here before and we hope he adheres to the deal.”

By contrast, Mr Meacher said that there was still some way to go before the final details were ironed out. “We are moving towards what I hope will be an agreement. I think it’s jumping the gun to say there is an agreement at the moment though. I do think we will reach an agreement along those lines. The important thing is there is a single centre-left candidate.”

One Labour source said that Mr Meacher originally had the better chance of getting on the ballot paper but his campaign has been less effective at gathering support among MPs than that of Mr McDonnell.

It was not clear last night that either candidate would get the backing of 44 MPs, even if one stepped down.

However, some Labour figures believe that a challenge from the Left could encourage a third challenge from someone such as Charles Clarke or John Reid, neither of whom want to see the hard-Left dominate the headlines in the leadership election. David Miliband recently announced that he would not stand, to the irritation of some hard-line Blairites, who are less keen that the Chancellor takes the crown.

Mr Meacher entered the contest in February promising a left-wing agenda. He called for Trident nuclear weapons to be scrapped, huge investment in renewable energy, curbs on City bonuses and nationalisation of the railways. He previously claimed to have enough support from MPs to get on the ballot and has always maintained that he has a chance of winning.

Mr McDonnell is a hero of the left-wing Campaign group, and has toured Britain since July gathering support from the unions and the membership. He claimed to have 22 backers, including Jeremy Corbyn, Mike Wood and David Drew. Mr McDonnell has campaigned on the basis that Labour needs rebuilding, the unions need strengthening and the influence of new Labour must be challenged.

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