Jeremy Corbyn has pulled out of cross-party Brexit talks with the government, saying the Tories are too “unstable” to do a deal with.
The Labour leader said his party would consider any further proposals from the government seriously, but told Theresa May in a letter than talks had “gone as far as they can”.
It comes as a leaked memo from the Labour-Tory discussions suggested a series of indicative votes on a customs union relationship between the UK and EU could take place next week, although Labour sources said the party had not signed up to the plan.
The government has said it will bring forward legislation to implement Brexit at the start of June, whether or not there is a deal with Labour.
Both parties are suffering in polling ahead of next week's European elections, with the latest survey putting Labour in third and the Tories in fifth as Nigel Farage's Brexit Party builds a commanding lead and the Liberal Democrats and Greens pick up pro-EU votes.
“I am writing to let you know that I believe the talks between us about finding a compromise agreement on leaving the European Union have now gone as far as they can,” Mr Corbyn wrote to the Prime Minister on Friday morning.
He said the talks had been “conducted in good faith on both sides” and were “detailed, constructive and have involved considerable effort for both our teams”.
“However, it has become clear that, while there are some areas where compromise has been possible, we have been unable to bridge important policy gaps between us,” he went on.
“Even more crucially, the increasing weakness and instability of your government means there cannot be confidence in securing whatever might be agreed between us.”
Mr Corbyn said there was “growing concern” on the Labour benches “about the government's ability to deliver on any compromise agreement”.
The Labour leader said: “As you have been setting out your decision to stand down and Cabinet ministers are competing to succeed you, the position of the government has become ever more unstable and its authority eroded.
“Not infrequently, proposals by your negotiating team have been publicly contradicted by statements from other members of the Cabinet.
“In recent days we have heard senior Cabinet ministers reject any form of customs union, regardless of proposals made by government negotiators.”
Mr Corbyn concluded that it was “only right that the Government now wishes again to test the will of Parliament” and said Labour would “carefully consider any proposals the Government wishes to bring forward to break the Brexit deadlock”.
“However, I should reiterate that, without significant changes, we will continue to oppose the Government's deal as we do not believe it safeguards jobs, living standards and manufacturing industry in Britain,” he said.