Jeremy Corbyn will face pressure to commit Labour to a confirmatory referendum on any Brexit deal when his party’s governing body meet later to agree its European election manifesto.
The ruling National Executive Committee is to gather on Tuesday for a crunch meeting to finalise the party’s position on Brexit for next month’s polls.
It comes as cross-party talks aiming to break the impasse continue, with the de facto deputy prime minister David Lidington describing discussions on Monday as “positive” and “productive”.
However, Foreign Secretary Jeremy Hunt said questions remained as to whether Labour was “serious about delivering Brexit”.
The EU’s chief Brexit negotiator Michel Barnier said he hoped to see results this week from the talks, and reiterated a call to “fix Brexit quickly”.
Ahead of the NEC meeting, Labour MPs Peter Kyle and Phil Wilson wrote to Mr Corbyn and all NEC members urging them to ensure that a confirmatory ballot is in the manifesto.
Mr Wilson told the Press Association that a referendum was backed by the majority of Labour MPs, MEPs, members and supporters and had featured in the policy approved by conference last autumn.
Labour MPs had twice been whipped in the Commons to support a motion tabled by the pair to require any Brexit deal to be subject to a public vote, he said.
“Three years on, we know more about what Brexit means and people should be allowed to compare what the deal is with what they were promised and decide whether they want to go ahead,” said Mr Wilson.
“If we don’t do it, the coming years will be divisive because people will be turning round and saying ‘Hang on, I didn’t vote for this’.”
Some 115 MPs and MEPs signed a letter to NEC members organised by the Love Socialism, Hate Brexit group urging them to explicitly back a referendum in the manifesto.
Deputy Labour leader Tom Watson used his Twitter account to urge followers to lobby NEC members to back a public vote.
And an additional 12 Labour candidates in the European elections added their names overnight to a pledge to campaign for a referendum and then back efforts to remain in the EU, bringing the total to 34 out of 70.
Meanwhile, some of Labour’s biggest union backers are also throwing their weight behind a referendum pledge.
TSSA general secretary Manuel Cortes said: “Frankly it’s time for our party to act on the overwhelming wishes of its members and voters by pledging to support a confirmatory public vote on any Brexit deal.
“We will be pushing hard for this to be included in Labour’s European manifesto.”
GMB general secretary Tim Roache said: “Any final Brexit deal must be put to the people for them to decide whether or not it’s acceptable.”
Corbyn-backing Labour MP Lloyd Russell-Moyle warned that a failure to offer a referendum could scotch the party leader’s chances of getting to 10 Downing Street.
“Only way JC will be PM is to offer a confirmatory vote – we could be out of power for a generation and the left will be swept away in Labour,” warned the member for Brighton Kemptown. “This is the fight for the left project and many are committing self harm.”
Change UK – the Independent Group – will hold the first of its “People’s Vote Remain” rallies calling for a second referendum in London on Tuesday.
On Monday, Mrs May’s effective deputy David Lidington and Chancellor Philip Hammond led the Government side in talks in Whitehall with a Labour team including shadow Brexit secretary Sir Keir Starmer and shadow chancellor John McDonnell.
Mr Lidington said Monday’s talks were “positive” and “productive”, the BBC reported.
However, Mr Hunt appeared to warn the Prime Minister and his Cabinet colleagues that a deal with Labour would alienate Tory MPs, preventing a deal clearing Parliament.
He told the Daily Telegraph: “There is always a danger of doing a deal with Labour that (means) you lose more Conservative MPs than you gain Labour MPs, but I think the essential question is whether Labour are serious about delivering Brexit.”
The Foreign Secretary, who is on a trip to Africa, also said he found it “very difficult” to imagine that the two sides would announce a compromise.
Alluding to David Cameron and Nick Clegg’s first joint press conference in the grounds of Downing Street in 2010, Mr Hunt said: “By all accounts, while they (the talks) have been more detailed and productive than we thought and expected, it’s still going to be very difficult to imagine a rose garden moment.”