THERESA May has set a seven-day deadline for Brexit talks with Labour to reach a conclusion.

A UK Government source said the discussions – which have been ongoing since early last month – need to be brought to a conclusion one way or another by the middle of next week.

Senior frontbenchers from both the Conservatives and Labour met for the latest round of talks yesterday and a spokesman for the Prime Minister said they had been “serious and constructive”.

“Further talks will now be scheduled in order to bring the process toward a conclusion,” he said.

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However, according to reports yesterday, the Whitehall source insisted the negotiations could not go on indefinitely.

Labour have been using the talks to press their case for backing a customs union with the European Union – a move that would anger many of May’s Brexiteer MPs who believe it would stop the UK striking post-Brexit trade deals.

Speaking after the weekly meeting of May’s Cabinet, the PM’s spokesman said: “Cabinet discussed the need to secure safe passage of the Withdrawal Agreement Bill as soon as possible in order to deliver on the result of the referendum.

“There’s an understanding on the need to make progress on delivering Brexit the way to leave the European Union with a deal is by securing safe passage of the WAB.”

He added: “I would point you to the need to make progress as soon as possible.”

Foreign Secretary Jeremy Hunt has meanwhile described weeks of discussions between the two parties as “more detailed and productive than we thought and expected”.

But he warned that some Conservative MPs could be forced to drop their support for the Prime Minister’s Brexit deal if she gives too much ground to Labour.

Hunt told The Telegraph: “There is always a danger of doing a deal with Labour that [means] you lose more Conservative MPs than you gain Labour MPs, but I think the essential question is whether Labour are serious about delivering Brexit.”

May’s Brexit deal has been defeated three times in the Commons in votes this year.