Boris Johnson’s Brexit plans have been dealt a fresh blow as crucial talks with Brussels were postponed after EU leaders agreed his plans “do not provide a basis” for a deal.

With just two weeks to go until a crunch EU summit, the prime minister had hoped to spend the weekend ramping up negotiations around his suggestions for a replacement to the Irish border backstop.

But European diplomats snubbed the request amid concerns the plans fell short, instead saying the UK could present new proposals next week.

The row comes as the majority of Northern Irish political parties said Mr Johnson’s plans showed “blatant disregard” for their people.

David Frost, the prime minister’s Brexit negotiator, was in Brussels on Friday for meetings but further talks have been put on ice until next week.

A European Commission spokesman said: “We gave our initial reaction to the UK’s proposals and asked many questions on the legal text.

“We will meet again on Monday to give the UK another opportunity to present its proposals in detail.

“We will continue to debrief the European parliament and the council, in line with our transparency policy.

“The commission will debrief the council working party this afternoon. Michel Barnier debriefed [EU member state ambassadors] yesterday, where member states agreed that the UK proposals do not provide a basis for concluding an agreement.”

An EU diplomat told The Times: “If we held talks at the weekend it would look like these were proper negotiations.

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“We’re still a long way from that. We need to work out quickly whether there is the opportunity to close that gap.”

The prime minister is expected to make a diplomatic push next week with work under way to set up a whistle-stop tour of European capitals.

It comes after Mr Johnson insisted on Friday that he would not delay Brexit despite his lawyers saying he will comply with a law calling for the October 31 exit date to be postponed if there is no deal.

Bombshell legal documents revealed the prime minister has accepted he must send a letter to Brussels requesting a delay to Brexit if no deal is agreed by 19 October, Scotland’s highest civil court heard.

But the PM later said the options facing the country were his proposed new Brexit deal or leaving without an agreement, “but no delay”.

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Brussels hardened its rhetoric against the latest plan, warning that it is up to the UK, not the EU, to fix “problematic” aspects of it before negotiations can start in earnest.

Asked whether Steve Barclay, the Brexit secretary, was right to say that the ball was “in the EU’s court” following the release of the proposals, a commission spokesperson said the EU would not be left “holding the bag” and that it was the UK that needed to act.

“We would disagree,” she told reporters in Brussels. “There are, as we have said, problematic points in the United Kingdom’s proposal and further work is needed – but that work needs to be done by the United Kingdom and not the other way around.

“We would remind you that it’s the UK leaving the European Union and not the EU leaving the UK.