Tom Watson is on course for a fresh clash with Jeremy Corbyn as he demands that Labour backs holding another Brexit referendum before any general election.
The party’s deputy leader will say an election on the single issue of the EU may not break the deadlock in Parliament.
Labour leader Mr Corbyn has made clear his priority is for an election once no deal is off the table, but Mr Watson will argue that the only way to end the impasse is with a second vote.
Speaking in London on Wednesday, Mr Watson will say: “My experience on the doorstep tells me most of those who’ve deserted us over our Brexit policy did so with deep regret and would greatly prefer to come back; they just want us to take an unequivocal position that whatever happens we’ll fight to remain, and to sound like we mean it.”
He will also call on Labour commit “unambiguously” to campaigning for Remain if a referendum were to follow an election.
Labour’s deputy leader’s comments come after Boris Johnson’s motion for an early election was twice defeated in the Commons. Opposition MPs refused to back the bid while the risk of no deal remained.
Mr Corbyn has said while an incoming Labour government would hold a new referendum – with Remain and a “credible” option for Leave on the ballot paper – he has yet to say which he would support.
However, Mr Watson will argue it is not too late for Labour to win back Remain voters put off by confusion over the party’s position on Brexit, if they were to commit clearly to campaign to stay in the EU.
Mr Watson will say that so much has changed since the original referendum in 2016 it was “no longer a valid basis” for determining Britain’s future and the priority should be a new public vote before an election.
“Very difficult though it was, I and many others respected the result of the 2016 referendum for a long time,” he said.
“But there eventually comes a point – and we are very far past it now, well into the fourth year since the referendum – when circumstances are so changed, when so much new information has emerged that we didn’t have in 2016, when so many people feel differently to how they felt then, that you have to say, no, that years-old plebiscite is no longer a valid basis on which to take such a momentous decision about the future of the United Kingdom.
“The only proper way to proceed in such circumstances is to consult the people again.”
Conservative Party chairman James Cleverly said: “Labour’s deputy leader makes clear Labour want to cancel the referendum result.
“This latest trick would mean delaying Brexit again for up to a year, handing over £250 million a week to Brussels for no purpose. Labour are running scared of an election and only offer more dither and pointless delay.
“Only Boris Johnson and the Conservatives will deliver Brexit by 31 October, no ifs or buts, so we can move on and focus on the issues that matter to people – investing in the NHS, reducing violent crime and cutting the cost of living.”