Split emerges in Momentum over whether to back Corbyn’s position as Unison says it will back pro-remain motion

Labour’s rows over Brexit worsened on Monday, as a split emerged in Momentum over whether to back Jeremy Corbyn’s position and Unison said it would back the pro-remain motion instead.

Before crucial votes on Labour’s Brexit position at the party’s autumn conference in Brighton, the leadership was desperately trying to shore up support for the policy of delaying a decision on how the party would campaign in a referendum until after an election.

The party’s largely pro-EU membership will vote first on whether to support Corbyn’s position, then a more neutral motion expressing backing for Corbyn and finally a statement in favour of Labour having a clear position in favour of remaining in the EU.

Pro-remain campaigners received a boost after Unison, one of the biggest unions, said it would be backing the motion in favour of campaigning to stay in the EU.

But they believed it would be “tight” because of a huge effort by the party leadership and unions to get delegates to support Corbyn’s position, which was endorsed by the national executive committee (NEC) on Sunday.

Momentum, the grassroots group of Corbyn supporters, decided during a phone meeting on Monday morning to support the leadership and reject the remain motion.

But the decision was not supported by Jon Lansman, the chair of Momentum and one of its co-founders, who said he was “completely supportive of Jeremy’s leadership but incredibly disappointed with the process by which the NEC statement on Brexit was produced … there was no meeting, no discussion, no consultation with the membership”.

“On one of the biggest issues of the day, this is a travesty. Across the membership there are many different views on Brexit, and on conference floor members should feel free to vote with their conscience,” he added.

It is understood the Labour leader’s office had been working behind the scenes to put pressure on Momentum officers to back Corbyn’s position and reject a clear remain stance.

The vote, expected in the late afternoon or early evening on Monday, will pitch Corbyn, Momentum, and some of the biggest unions including Unite and the GMB, against much of the party’s membership, shadow cabinet ministers such as Emily Thornberry, and Unison.

Earlier, John McDonnell, the shadow chancellor, made clear he wanted to campaign to remain in any second referendum, but he attempted to play down the row on Monday by saying he was happy to delay a decision on how the party would campaign.

“I smiled when you used the language earlier of civil war and revolt but there isn’t any war in the Labour party. It’s about honest, democratic debate,” he told BBC Radio 4’s Today programme.

“People have high emotions on this because they feel it’s important. But that’s people respecting each other’s views as well. I keep saying: do not mistake democracy for division. It isn’t – what we’re having is an honest debate.”

He did, however, differ from Corbyn in saying he believed that no future deal could be better than Britain staying in the European Union.

McDonnell said he wanted Labour to continue to promise an EU renegotiation, followed by a second referendum, if it won the next election.

McDonnell also described the decision of Andrew Fisher, a key policy aide to the leader, to quit his post as the result of “a bad day at the office”.

Fisher, who masterminded the party’s 2017 manifesto, said he no longer had faith that Labour would be successful. He wrote in a memo to colleagues that members of Corbyn’s team had a “lack of professionalism, competence and human decency”.

“Sometimes you are going to have a bad day at the office. Sometimes your colleagues are going to drive you up the wall,” said McDonnell, who added that Fisher was one of his closest friends and that he would attempt to persuade him to remain in the role.