Donald Tusk, the European council president, has ratcheted up the pressure on Theresa May by rejecting the Chequers plan and warning of a breakdown in the Brexit talks unless she delivers a solution for the Irish border by October – a deadline the British prime minister had already said she will not be able to meet.

Chequers unacceptable because it would undermine single market, say EU leaders as summit ends - Politics live Read more

The stark threat to unravel the talks came as the French president, Emmanuel Macron, broke with diplomatic niceties and accused those of backing Brexit of being liars. “Those who explain that we can easily live without Europe, that everything is going to be all right, and that it’s going to bring a lot of money home are liars,” he said.

“It’s even more true since they left the day after so as not to have to deal with it.”

The comments came at the end of a leaders’ summit in Salzburg, where May had appealed for the EU to compromise to avoid a no-deal scenario. She had been hoping to take warm words over Chequers into Conservative party conference.

Tusk, who moments before his comments had a short meeting with the prime minister, told reporters that he also wanted to wrap up successful talks in a special summit in mid-November.

But, in a step designed to pile pressure on the prime minister, he said this would not happen unless the British government came through on its commitment to finding a “precise and clear” so-called backstop solution that would under any future circumstances avoid a hard border on the island of Ireland.

“Without an October grand finale, in a positive sense of this word, there is no reason to organise a special meeting in November,” Tusk said. “This is the only condition when it comes to this possible November summit.”

The EU couldn’t help May at Salzburg because she’s seeking the impossible | Rafael Behr Read more

The deadline of the weekend of 17 and 18 November on the Irish issue is a looming threat to May, who had told the Irish prime minister, Leo Varadkar, earlier in the day that she did not think it was possible by the October summit for her government and the EU to come to a compromise on the issue.

The EU has proposed that Northern Ireland in effect stays in the single market and customs union as the rest of the UK withdraws. The prime minister insists she will not sign up to such a plan, which she claims would economically and constitutionally “dislocate” the UK.

Tusk also offered a withering assessment of the economic proposals in the Chequers plan, under which the UK would have a common rulebook with the EU for goods, and benefit from frictionless trade and an independent commercial policy through a bespoke customs arrangement.

“It must be clear that there are some issues where we are not ready to compromise and first of all this is our fundamental freedoms and single market and this is why we remain sceptical and critical when it comes to this part of the Chequers proposals,” he said.

Macron dismissed May’s suggestion that Chequers was the only solution other than a no-deal scenario.

He said of the white paper: “It was a good and brave step by the prime minister. But we all agreed on this today, the proposals in their current state are not acceptable, especially on the economic side of it. The Chequers plan cannot be take it or leave it,” he said.

The German chancellor, Angela Merkel, agreed during her press conference that “substantial progress” was needed on the UK’s withdrawal agreement by the next European council meeting in October in order to pave the way for it to be finalised at a special summit in November.

Merkel said there was “still a large piece of work” on the separate issue of future trade relations with the UK. The EU27 was “united that, in the matter of the single market, there can be no compromises”, she said.

“No one can belong to the single market if they are not part of the single market.”