LIVERPOOL, England (Reuters) - Britain’s opposition Labour Party is set to vote against any deal Prime Minister Theresa May clinches with the European Union and is open to a second referendum with the option of staying in the bloc, Brexit spokesman Keir Starmer said on Tuesday.

The Labour Party's Shadow Secretary of State for Departing the European Union Keir Starmer walks to a radio interview at his party's conference in Liverpool, Britain, September 25, 2018. REUTERS/Hannah McKay

With just over six months until Britain leaves the EU, May has yet to reach a deal on the terms of the divorce, and her plan for future trade ties has been rebuffed by both the EU and many in her own Conservative Party.

May says she will press on with her proposals, and branded Labour’s intention to vote against any agreement that falls short of its demands as “not in the national interest”.

Labour has listed six tests it would apply to any Brexit deal, including a strong future relationship with the EU that delivers the same benefits Britain has as a member of the bloc’s single market and customs union.

Starmer said May was on course to fail these tests.

He called for an election to allow a Labour government to steer Britain’s departure from the EU, the biggest shift in the country’s foreign and trade policy in decades.

“If Theresa May brings back a deal that does not meet our tests - and that looks increasingly likely - Labour will vote against her deal,” he told Labour members at the party’s conference in the northern city of Liverpool.

He repeated Labour’s argument that if parliament rejects May’s Chequers deal, named after the prime minister’s country residence where she hashed out a plan with her ministers, the party would press for a general election.

“But if we need to break the impasse our options must include campaigning for a public vote and nobody is ruling out ‘remain’ as an option,” he said to a prolonged standing ovation in a packed conference hall.

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Labour leader Jeremy Corbyn backed his Brexit spokesman, but declined to say which way he would vote in a possible second referendum because “it depends what the question is”.

“We will challenge this government. If they don’t meet our six tests, we will vote against it, and then we will take it from there,” he said in a television interview.

TEARING UP PLEDGE

An internal EU document seen by Reuters on Tuesday reiterated the bloc’s rejection of Chequers, saying it would “give the UK an unfair competitive advantage”, but it welcomed her proposal of a free-trade are” as “the starting point”.

As for a possible new referendum, EU officials have voiced their doubts.

“That does not sound like a solution to anything. The first referendum is still keeping us busy. And will they want to have a third one in another two years?” asked a senior EU diplomat in Brussels. “It’s more about power struggles in Britain than about managing Brexit seriously.”

May, speaking to reporters on her way to the U.N. General Assembly in New York, said Labour would hurt the country by opposing any deal “regardless of how good it is for the UK,” accusing the party of being ready to “accept any deal Europe gives, regardless of how bad it is”.

“That’s not in the national interest. What we’re doing is in the national interest.”

But with May’s plan for maintaining close ties with the EU for trade in goods facing opposition from her own lawmakers, she is aware of the crucial role Labour could play in getting a deal through parliament.

May has a working majority of just 13 in the 650-seat parliament and a former junior minister said this month as many as 80 of her own lawmakers were prepared to vote against a Brexit deal based on the Chequers plan.

But like her Conservatives and much of the country, Labour is split over how to leave the bloc, with veteran eurosceptic Corbyn under pressure from many members to move to a more pro-EU position.

Brendan Chilton, general secretary of Brexit campaigning group Labour Leave, accused Starmer of launching a leadership bid.

“This is a betrayal of the very highest order. It is a betrayal not only of the millions of Labour voters, but of our 2017 manifesto,” he said, referring to the party’s campaign at last year’s election in which it won more votes than expected.

Labour’s conference passed the motion with a show of hands on Tuesday to keep a second Brexit referendum as an option if May fails to get her Brexit plan through parliament.

The motion reiterates Labour’s position on Brexit: it wants full participation in the EU’s single market and will reject a “no deal Brexit”.

The wording on a possible second referendum is left vague. The party’s finance spokesman, John McDonnell, said any such vote should be on how - not whether - to leave the EU.

But Starmer was clear: the motion could allow Britain to vote to stay in the EU.

“This isn’t about frustrating the process,” he said. “It’s about stopping a destructive Tory Brexit. It’s about fighting for our values and about fighting for our country.”