TWO senior Labour frontbenchers have thrown their weight behind calls for a second referendum on a cross-party Brexit deal to gain the backing of their MPs.

Shadow Brexit secretary Sir Keir Starmer warned it was “impossible” to see how an agreement between the Conservatives and his party could clear the Commons unless it guaranteed the deal would be put back to the public for a “confirmatory vote”.

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And Labour’s deputy leader Tom Watson said he thought the way out of the impasse was a “confirmatory ballot” on Theresa May’s agreement, saying it would be “difficult” for his party to assist in the UK’s exit from the EU without another referendum.

Ahead of the continuation of cross-party talks yesterday afternoon, Starmer told the Guardian that “probably 120 if not 150” of the party’s 229 MPs could vote against the deal unless it was linked to a referendum.

And he said: “I’ve made it clear that at this stage, at this 11th hour, any deal that comes through from this Government ought to be subject to the lock of a confirmatory vote.”

Watson told BBC Radio 4’s Today programme: “If a deal could be found that inspires enough votes in Westminster then fine, but it seemed to me that that’s very, very difficult. And so 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.”

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Watson also described Labour’s position in relation to the European elections as a “Remain and reform” party.

Last month Jeremy Corbyn saw off an attempt to commit the party to a confirmatory referendum on any Brexit deal, and Labour will instead only back a fresh vote only if it cannot either win the changes it wants to May’s deal or secure a General Election.

Nigel Farage later said the idea of a confirmatory referendum was the “most outrageous proposal” he had ever seen and would lead to a party like the Brexit Party winning a majority in Parliament at the next General Election.

Speaking during a walkabout in Pontefract, part of Labour MP Yvette Cooper’s constituency, Farage said: “A confirmatory vote, it sounds all nice and fluffy, what does it mean?

“It means we stay in the European Union as we are, or we nominally leave and stay permanently part of a customs union and with single market rules. They wouldn’t even give the public the option of actually leaving. It’s the most outrageous proposal I’ve ever seen.

“It wouldn’t break the deadlock, it would just mean we’re not leaving the European Union. It would just mean, basically, the second referendum would be there, giving two choices to reverse the result of the first one. It’s an outrage, it cannot happen.

“I promise you this, if we get forced as a country into that choice of a referendum, there’ll be bigger change in British politics than anybody can even imagine.”

He added: “If the Labour Party and sections of the Tory party were to completely sell-out on any idea of a clean break then the Brexit Party, or something like it, would win a huge number of seats at the next General Election and undoubtedly hold the balance of power in Westminster.”

Watson’s description of the party as one of “remain and reform” appear at odds with comments by fellow frontbencher Barry Gardiner who said recently that Labour was “not a Remain party now” and that the leadership was “committed” to leaving the bloc.