Labour would “carry out whatever the people decide” in another referendum on Brexit, says Jeremy Corbyn.
The party leader told the Guardian he would hold a fresh vote if he became PM – offering a Labour-negotiated deal and Remain on the ballot paper.
Mr Corbyn said the pledge made Labour “the only UK-wide party ready to put our trust in the people of Britain”.
It comes ahead of Labour’s party conference where he is expected to face increasing pressure to back Remain.
According to campaign group Another Europe is Possible, more than 80 motions have been submitted by local Labour groups for debate at conference in Brighton calling for the party to back Remain in a future public vote.
A number of high profile members of the shadow cabinet, including shadow foreign secretary Emily Thornberry and shadow chancellor John McDonnell, have said they would campaign for Remain.
Labour’s deputy leader, Tom Watson, has called for another public vote on Brexit before any general election.
Earlier this week, the Liberal Democrats agreed a new manifesto pledge that if they won a majority government in a next election, they would scrap Brexit altogether without another vote.
But their leader, Jo Swinson, said they would continue to call for another referendum alongside other opposition parties until an election was called.
Prime Minister Boris Johnson says he wants to secure a deal with the EU before the Brexit deadline of 31 October – but the UK will leave on the date “do or die”.
This is despite MPs passing a law to block a no-deal Brexit, which forces the PM to write to the EU and ask for an extension if a deal hasn’t been agreed by Parliament before 19 October.
‘Bring people together’
In the Guardian interview, Mr Corbyn reiterated Labour’s four sticking points for a “sensible” deal with the EU – namely a new customs union, a close single market relationship, guarantees of workers’ rights and promises on environmental protections.
Once these were secured, he said they would put that deal to a vote against Remain, adding: “I pledge to carry out whatever the people decide, as a Labour prime minister.”
Mr Corbyn said Mr Johnson wanted to “crash out” of the EU without a deal, while the new position of the Lib Dems would be a “parliamentary stitch-up” and “simply undemocratic”.
He added: “Labour is the only party determined to bring people together.”
But Michael Chessum, national organiser for Another Europe is Possible, said Labour members were the party’s “the secret weapon” at a general election, and Mr Corbyn “ignores them at its peril”.
“Support for an explicit Remain stance is evidently overwhelming,” he said.
“Only if Labour can get clarity on this part of its policy can fight the election on its domestic agenda.”
End of Labour Students
Meanwhile, the party’s National Executive Committee has voted to scrap its affiliation with Labour Students – which, up until now, had been the official student wing of the party.
Earlier, the chair of Labour’s Momentum campaign group, Jon Lansman, put a motion to the NEC calling for it to set up a new student body.
BBC political correspondent Iain Watson says the motion has now passed, but the group has called the move an attack on party “centrists”.