Labour must be ready to throw its full support behind another referendum on Brexit, its deputy leader Tom Watson says today, as a new poll shows 86% of party members want the British people to be given a final say on the UK’s future relationship with Europe.

In an interview with the Observer, Watson says that with the likelihood of a general election growing after Theresa May’s humiliation at the EU summit in Salzburg last week, it is vital the Labour leadership and membership unite to maximise the chance of dislodging the Tories from office.

Watson says that while he would prefer Brexit to be debated in an election soon, he is clear that the views of the membership in favour of another public vote must be respected.

“Jeremy and I were elected in 2015 to give the Labour party back to its members,” he says. “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.” He added: “That is what happens when you return the party to the members.”

Asked if this should mean Labour commits to another national vote in its next election manifesto, he said: “There is going to be pressure in the system for that to happen.”

Watson’s willingness to support a second referendum contrasts with the more cautious approach of Corbyn and the shadow chancellor John McDonnell, and sets the stage for a potentially explosive debate on Brexit in Liverpool on Tuesday.

Tom Watson: ‘If Labour members call for a people’s vote on Brexit, then we must respect that’ Read more

In an interview with the Guardian on Saturday McDonnell said that while he did not rule out backing a people’s vote, he was worried that re-running arguments about the UK’s EU membership might encourage Ukip and the far right to stir up xenophobic feeling in the country.

Corbyn-supporting delegates warned that if their demands were rejected, “disillusionment” would spread fast across the movement that propelled him to the leadership. Alena Ivanova, a Momentum activist and organiser for one of the groups pushing for another vote, Another Europe is Possible, said: “The main question at this year’s conference is about democracy and whether members really control Labour. There is a huge groundswell among members to shift Labour policy, fight Tory Brexit and give people control over their own destinies by giving them the final say. If the overwhelming view of members is not reflected in the outcomes of conference, if there is no shift in Labour’s policy, that will produce a wave of disillusionment at the grassroots and the consequences for the movement could be bad. We would be failing to grasp a historical opportunity.”

Labour’s national executive committee has decided to recommend the creation of an additional deputy leadership post, raising the prospect of a candidate standing on a platform of a new EU referendum. If they get that mandate, the pressure on the existing leadership to change position could reach boiling point.

Corbyn himself has said he will back a second Brexit referendum if it is supported by the Labour party conference. In an interview with the Sunday Mirror he said: “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.”

Those supporting another referendum are bound to seize on the findings of a YouGov poll of 1,054 Labour members, commissioned by the People’s Vote campaign and published on Sunday, which shows huge support both for the UK to remain in the EU and for another referendum on the outcome of Brexit negotiations.

About 90% of Labour members say they would vote to remain in the EU if there were a referendum now, while 86% back a public vote on the outcome of the negotiations, with just 8% against. Support for another referendum stands at 93% in London among Labour members, 82% in the rest of the south, and 86% in the north. The poll also revealed that should a general election be called, 74% of members want a commitment for a new referendum included in Labour’s manifesto.

Corbyn and the shadow cabinet want the conference to focus on Labour’s radical economic agenda, and plans to boost equality. Speaking at the Labour Women’s conference on Saturday, Corbyn said: “The Tories may talk about equality. They may say their government delivers for all, but the lived experience of women in Britain tells a different story. Labour is the party of equality, the party of women, the party committed to measuring all our policies on their impact on women in society.”

But rows over Brexit threaten to dominate the party conference. More than 140 motions on Brexit have been submitted by local parties and unions, many of which call for Labour to commit to another referendum.

The Observer understands that Labour’s Brexit spokesman, Keir Starmer, will meet the national co-ordinating group of Momentum on Sunday as part of attempts to broker a last-minute compromise.

Watson also uses his interview to reject calls from what he calls “small groups” in Labour who want to change its rulebook to make it easier to deselect MPs. He is strongly opposed to “mandatory deselection”, which he says would be hugely divisive when the party should be coming together.

Corbyn faces clash with Labour members over second EU referendum Read more

He argues that the change would prevent Labour MPs from fighting the Tories as they would be preoccupied with fighting battles in their local branches. He says the party should be able to reflect a diverse range of views. “Labour has only ever succeeded as a broad church, and the country needs us to be a broad church at this crucial point in our nation’s history.” he says. “It is up to me and Jeremy to unify this party.”

The GMB union general secretary, Tim Roache, will speak at a march in Liverpool on Sunday for a people’s vote. Also at the event will be the Labour MP David Lammy, who said: “A people’s vote is not only the right thing to do for jobs, public services and the future of our young people – it’s the best way to get a radical Labour government.”