EU chiefs have held "significant" Brexit talks with Jeremy Corbyn and Keir Starmer.

Europe wants assurances Labour will honour Conservative Party commitments.

Scottish Tory leader Ruth Davidson has told Theresa May's critics to "put up, or shut up."

LONDON — The EU is holding private talks with Jeremy Corbyn amid fears Theresa May's government could crumble at any minute, according to The Daily Telegraph.

Sources told the newspaper that there has been a "significant change in tone" in Europe's dealings with Labour amid fears that a collapse of the British government could take Brexit talks back to square one.

The Telegraph said Labour leader Corbyn and shadow Brexit Secretary Keir Starmer have held more than one meeting with Michel Barnier, the EU's chief Brexit negotiator, and Frans Timmermans, the first vice president of the European Commission.

The EU leaders reportedly want assurances from Corbyn that he will honour the commitments set out by the Conservative Party. These include pledges to continue paying into the EU budget and allowing freedom of movement after Brexit day in March 2019.

Corbyn met with Barnier in July to set out Labour's Brexit vision. At the time, he said Labour was "ready to take up the responsibility for Brexit negotiations" if there was a change in government.

The news emerged after a tumultuous week for Prime Minister May, in which a chaotic party conference speech has laid bare the divisions in her party. Former party chairman Grant Shapps led what looks to be an unsuccessful plot to oust the PM, who was handed a P45 on stage by prankster Simon Brodkin during her conference address on Wednesday.

But Shapps' plan was openly ridiculed by some Tory MPs and May said on Friday that she has the "full support of the cabinet." Home Secretary Amber Rudd and Environment Secretary Michael Gove were among the senior ministers to publically back May.

Ruth Davidson. Jeff J Mitchell / Getty

And on Saturday, the increasingly influential Scottish Tory leader Ruth Davidson told the party's rebels to "put up, or shut up." Speaking on Radio 4's "Political Thinking" podcast, Davidson said the Conservatives should focus on governing.

"I think if the plotters were serious, they would be led by someone a bit more serious," she said, in a withering remark about Shapps. This was echoed by influential backbench MP Nigel Evans, who told "BBC Breakfast" that Shapps' "sniping" was not helping the party.

Foreign Secretary Boris Johnson, the man seen by many as the favourite to replace May, has also called on Conservative MPs to get behind the prime minister. In a message to an MPs' WhatsApp group, he said it was time to "circle the wagons and turn the fire on Corbyn."

Henry Zeffman, a political reporter at The Times, tweeted Johnson's message: