Tom Watson: Labour is a remain and reform party on EU membership

The Labour deputy leader said he agreed with shadow Brexit secretary Sir Keir Starmer, that up to 150 of the party's 229 MPs would reject any agreement that did not include a second referendum.

But Mr Watson's stance on his party's approach to the EU appears to put him at odds with the party leadership and other frontbenchers.

Jeremy Corbyn's official position is to only back a fresh vote only if Labour cannot either win the changes it wants to Mrs May's deal or secure a general election, while shadow international trade secretary Barry Gardiner insisted that Labour was now a Brexit party.

West Bromwich East MP Mr Watson said: “We are a remain and reform party, but obviously when it comes to a deal, people could form their own view."

He added that while talks with the government over a compromise deal were ongoing, it “would be difficult” to get it through parliament without a new public vote.

“I think the difficulty is just parliamentary arithmetic,” he said.

“Keir Starmer has alluded to this today as well, John McDonnell did last week. The whipping arrangements for these deals are very difficult, as MPs have hardened their positions within their parties.”

Mr Watson said he had not changed his view that getting a Brexit deal though the Commons was the priority, but had come round to the idea of a second referendum for practical reasons.

He said: “I’ve wanted a deal. I reluctantly came to the view that there should be a confirmatory ballot, because I thought it was the only way we would break the impasse.

“If a deal could be found that inspires enough votes in Westminster, then fine. But it seemed to me that that’s very difficult.

“My idea of a confirmatory ballot is not a religious point, or a point of ideology, it’s just – how do you get an outcome, how do you sort this out?

"And one way to do it are these two minority positions – the Prime Minister's deal and those that think the people should have a say on the deal – plug them together and you build a majority."

It came as Mr Watson made a speech marking the 25th anniversary of John Smith’s death, in which he argued that the former Labour leader, as a pro-European internationalist, would have also backed a second referendum.

“If John was alive today, to witness the great damage this process is wreaking on country and our public debate, I have no doubt that he would have taken a stand very similar to that of his deputy, Margaret Beckett, and backed a people’s vote as a way out of this destructive mess,” he said.

Meanwhile in a separate speech to the Fabian Society, Mr Watson pleaded with supporters to back Labour in next week's European elections.

"There are only two forces that can win this election – that nasty nationalism of the Farage Brexit Party, or the tolerant, compassionate outward looking patriotism of the Labour Party," he said.

"I can only plead with Labour supporters – don't stay at home, don't put that cross elsewhere, don't let them win."

Talks between Labour and the government are continuing this week, despite claims suggesting they were doomed to failure.

Communities Secretary James Brokenshire dismissed the reports.

“These talks are very serious, yes – we wouldn’t have committed all of the time and effort on all sides in relation to this. They have been constructive, they have been detailed."

He said Sir Keir's comments were “a slightly different message to the core message that the Labour party has been giving about a second referendum”.

Mr Brokenshire added that he believed a second vote was a bad idea.

“These talks are about how to give effect to the referendum, how we give effect to leave the EU, not somehow reopening the debate all over again," he said.