TALKS between the Government and Labour to break the Brexit logjam have been “productive” and will continue today – but it was still unclear whether the Prime Minister was willing compromise on any of her red lines.

Theresa May and Jeremy Corbyn’s negotiating teams met for four-and-a-half hours in the Cabinet Office on Thursday for “detailed” talks.

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The talks are aimed at finding a consensus Brexit position ahead of a crunch summit of European Union leaders in Brussels on April 10.

David Lidington, effectively the deputy prime minister, led the Government’s negotiating team with Brexit Secretary Steve Barclay, Chief Whip Julian Smith, Business Secretary Greg Clark and Theresa May’s chief of staff Gavin Barwell.

On the other side of the table were shadow Brexit secretary Sir Keir Starmer and shadow business secretary Rebecca Long-Bailey along with senior Labour officials.

The National: De facto deputy prime minister David Lidington led the government's team in the talksDe facto deputy prime minister David Lidington led the government's team in the talks

A Downing Street spokesman said the “detailed and productive technical talks” were supported by civil servants.

“The Government and the Opposition hope to meet again tomorrow for further work to find a way forward to deliver on the referendum, mindful of the need to make progress ahead of the forthcoming European Council,” the spokesman said.

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But one shadow cabinet member told the Financial Times that the government had not proved it was “prepared to flex over any lines we have called for”.

Any decision on an extension to Brexit in order to prevent the UK crashing out of the EU on April 12 will be taken by EU leaders at that summit.

The talks in Westminster between the Government and Opposition have highlighted divisions within both the Tory and Labour ranks.

Backbench Labour MPs have issued a warning to Corbyn not to include a second Brexit referendum in any compromise deal thrashed out with May.

Arriving for the talks in Whitehall, shadow Brexit secretary Starmer confirmed that a “confirmatory” referendum was among the ideas on the table for discussion.

But a group of 25 Labour MPs wrote to Corbyn warning that a second public vote would “divide the country further and add uncertainty for business”.

They warned: “A second referendum would be exploited by the far-right, damage the trust of many core Labour voters and reduce our chances of winning a General Election,” they warned.

Signatories included veteran backbenchers Sir Kevin Barron, Dennis Skinner and Ronnie Campbell, former minister Caroline Flint and MPs for Leave-voting areas of the North and Midlands including Gloria De Piero, Sarah Champion and Gareth Snell. They said the policy adopted at Labour’s autumn conference made clear there was no need for a public vote if the party secures its preferred customs union deal, which was now “within reach”.

The letter reflects deep fissures within Labour over whether to demand a confirmatory vote as part of any compromise.

Deputy leader Tom Watson has said: “I don’t think our party would forgive us if we were to sign off on a Tory Brexit without that kind of concession.”

Meanwhile, a string of Cabinet ministers signalled that Tories could be prepared to compromise on Labour’s key demand of a customs union arrangement with the EU – an idea loathed by Brexiteers.

Attorney General Geoffrey Cox said avoiding a customs union was not an “article of faith”, while Chancellor Philip Hammond said Tories should be ready to look at it.

Health Secretary Matt Hancock told BBC Radio 4’s Today programme that he preferred May’s deal to a customs union, but added: “I have spoken about the problems of a customs union and I don’t think it’s as good for the country. But I also want to deliver Brexit.”