Donald Tusk demanded “concrete proposals” and “new facts” from Theresa May on how to end the deadlock over the Irish border, warning that a deal may not be possible without further movement from the UK. The warning came as Mrs May appealed for loyalty from her ministers, telling them to “stand together and stand firm” to deliver Brexit.

Former prime minister Sir John Major weighed into the mounting fears over a no-deal Brexit last night in his gravest declaration yet over the impact of EU withdrawal.

The ex-Tory leader described the 2016 referendum vote as a “colossal misjudgment” that could ultimately break up the UK.

PABest A mock customs post is set up at Ravensdale, Co Louth, as anti-Brexit campaigners hold a go-slow protest on the main road between Northern Ireland and the Republic of Ireland to highlight concerns about the impact on trade.

“It will damage our national and personal wealth and may seriously hamper our future security,” he said. “It may even, over time, break up our United Kingdom. It will most definitely limit the prospects of our young. And once this becomes clear, I believe those who promised what will never be delivered will have much to answer for. They persuaded a deceived population to vote to be weaker and poorer.”

At a three-hour meeting of the Cabinet yesterday, there were no threats of resignation from ministers unhappy at proposed compromises by the UK in search of common ground on the Irish border ‘backstop’.

However, the Cabinet was not asked to sign off on the Prime Minister’s plan, delaying a potential row with Brexiteers until after this week.

Mrs May will address the remaining 27 EU leaders before they have dinner in Brussels this evening to discuss her offer. Neither side has set out new proposals ahead of the summit on how to maintain the status quo along the Irish land border without introducing new checks on goods crossing the Irish Sea.

Speaking after being briefed by the EU’s chief negotiator Michel Barnier, Mr Tusk played down expectations of a breakthrough.

“As I see it, the only source of hope for a deal for now is the goodwill and determination on both sides,” Mr Tusk told a Brussels press conference.

“However, for a breakthrough to take place, besides goodwill we need new facts.

“I am going to ask Prime Minister May whether she has concrete proposals on how to break the impasse. Only such proposals can determine if a breakthrough is possible.”

Senior European Commission officials have cast doubt on the prospect of a special Brexit summit being declared for next month if there is no movement on the border issue. In Downing Street yesterday, the Prime Minister won support from Cabinet colleagues as she set out two key “sticking points” preventing the conclusion of a withdrawal agreement. Mrs May has offered to keep the whole UK in a customs union, but only for a temporary period.

In Luxembourg, foreign ministers from the remaining 27 EU states received a briefing from Mr Barnier, who said “more time” was needed to find an agreement that kept the Irish border open. Belgium’s foreign minister Didier Reynders put the chance of a no-deal Brexit at “50/50”.

Cabinet told to '˜stand firm' as Europe demands '˜new facts' to solve Irish riddle