Video report by ITV News Political Correspondent Paul Brand
Jeremy Corbyn said he is prepared to back a second EU referendum if activists at his party conference force a change in Labour policy.
His deputy, Tom Watson, confirmed to ITV News that Labour would back a second referendum on Brexit if members back it at the party's conference in Liverpool.
"Jeremy and I are keen that we have a proper debate on Brexit and of course we'll respect the decisions they make at the end of conference," Mr Watson said.
Asked by ITV News Political Correspondent Paul Brand if that meant the leadership would adopt a new stance if members back another public vote at conference, he said: "Of course we have to listen to our membership and it will be built into our policy positions going forward."
The leadership comments came as a poll found 86% of Labour members think voters should have the final say on Brexit.
Labour politicians joined thousands in a march through Liverpool on Sunday demanding a so-called People’s Vote.
Mr Corbyn, who favours an election over a referendum, is set to face intense pressure at the party’s annual conference to commit Labour to a second referendum.
Addressing thousands of supporters at a rally on Saturday night, he again indicated he would prefer a general election to another referendum.
"We've got big issues coming up in Parliament in the near future," he told the crowd, some of whom were waving EU flags.
"We will challenge this Government on whatever deal it brings back, on our six tests - on jobs, on living standards, on environmental protection and protection of those jobs and the ability of an incoming Labour government to invest and intervene in an economy to bring about decent wages, jobs and full employment.
"And if this Government can't deliver then I simply say to Theresa May: the best way to settle this is by having a general election."
A poll for The Observer found 86% of Labour members think voters should have the final say on the outcome of Brexit negotiations, and 90% would now vote to remain in the EU.
The Independent reported plans have been discussed within the party for a Commons vote of no confidence in the Prime Minister to force an election if she fails to get her Brexit plan through Parliament later this autumn.
But in an interview with the Sunday Mirror, Corbyn said he will back a second Brexit referendum if it is supported by the Labour Party conference.
"What comes out of conference I will adhere to. But I'm not calling for a second referendum, I hope we will agree that the best way of resolving this is a general election," he said.
Ahead of Corbyn's speech, Shadow chancellor John McDonnell told activists to be ready for an early election.
"The Tories hate each other now more than they hate us," he said.
"So I believe they could fall apart at any time."
MPs and union leaders are expected to join a march on the opening day of the conference on Sunday to demand a so-called “People’s Vote”.
And more than 100 constituency parties have submitted motions calling for the issue to be put to a vote. Many activists believe that with Mrs May’s plans in disarray following the rejection of her Chequers proposals by EU leaders in Salzburg, the time is now right for Labour to throw its weight behind a fresh ballot.
The YouGov survey of more than 1,000 Labour members found 86% support a referendum on the outcome of Brexit talks, against just 8% who oppose it.
Even in the North and Midlands, where many Labour constituencies voted Leave in 2016, there was overwhelming support – 86% and 88% respectively – for a second vote.
Some 81% believe their standard of living would get worse after Brexit and 89% said it would be bad for jobs.
Mr Watson told The Observer: “Jeremy and I were elected in 2015 to give the Labour Party back to its members.
“So if the people’s party decide they want the people to have a final say on the deal, we have to respect the view of our members and we will go out and argue for it.”
But shadow chancellor John McDonnell warned on Saturday that a second referendum could stoke racial tensions and far-right populism.
“I really worry about another referendum,” said Mr McDonnell.
“I’m desperately trying to avoid any rise of xenophobia that happened last time around, I’m desperately trying to avoid giving any opportunity to Ukip or the far-right. I think there’s the real risk of that.
“We’re not ruling out a people’s vote, but there’s a real risk, and I think people need to take that into account when we’re arguing for one.”
YouGov interviewed 1,054 Labour members between September 13 and 18.