Jeremy Corbyn will face a showdown with Labour members over Brexit policy as grassroots activists call for the party to back remaining in the European Union.
The Labour leader has called for a neutral position going into a general election, saying that he would negotiate a new Brexit deal with Brussels which would then be put to a referendum.
But activists in Brighton will vote on whether the party should campaign to stay in the European Union – even if that means rejecting a deal a Labour government has negotiated with the EU.
Instead separate motions are expected to be put to a vote, one calling for Labour to back remain and another endorsing a policy of neutrality.
A statement by Labour’s ruling National Executive Committee – pushed by Mr Corbyn – says the party should only decide how to campaign in a referendum at a special conference held after a general election.
After a meeting at the conference in Brighton aimed at agreeing the wording of a Brexit motion, activists campaigning for a remain position declared victory, despite the prospect of alternatives being put to a vote on Monday.
Andrew Lewin, founder of Remain Labour, told PA: “This is a huge step forward.
“Labour members will tomorrow have the chance to change party policy – so Labour commits to campaign to Remain in all circumstances.”
Mike Buckley, director of Labour for a Public Vote, said: “On Monday Labour conference will vote on a motion that, if passed, would commit the party to campaign for Remain in all circumstances. This reflects the opinion of the vast majority of our members and voters.
“Labour is already the only main party committed to a democratic vote on Brexit.
“If we add a commitment to Remain we will at last be providing the leadership the country needs, in contrast to the chaos offered by an increasingly extreme Conservative Party.”
The lengthy “compositing” meeting to agree the wording of motions followed a day of chaos over Labour’s Brexit stance.
Mr Corbyn’s NEC statement was emailed round the body and endorsed without a formal meeting, despite opposition from some members.
Unite union boss Len McCluskey, a key ally of the Labour leader, called on the party’s senior figures to fall in behind the policy or “step aside”.
Mr Corbyn suggested that it could be possible for the UK to be better off out of the EU.
It “depends on the agreement you have with the European Union outside”, he said.
But shadow foreign secretary Emily Thornberry – whose actions were singled out by Mr McCluskey – deputy leader Tom Watson and London Mayor Sadiq Khan insisted the party must throw its weight behind the remain cause now rather than at a special conference after an election.
Before the Brexit votes, shadow chancellor John McDonnell will deliver his keynote speech – and is expected to signal that Labour will scrap universal credit.
He will also confirm plans for Labour to fund free personal care for elderly people in England.
The pledge to fund free personal care – which would cost an estimated £6 billion a year in 2020/21 – would more than double the number of people receiving state-funded support, Labour said.
In a rally on Sunday night, Mr McDonnell indicated that a pledge to reform the social security system would be included in Labour’s first Queen’s Speech.
He said there has to be a proper social security “safety net”.
“That has to be on the basis of enabling people to have a decent quality of life with an adequate income.
“That has to mean getting rid of the bloody Universal Credit.”