The European Union believes a Brexit deal with the UK will not be struck by October.

This leaves massive question marks over whether the UK will actually be able to exit the EU in March, 2019.

A political logjam in Theresa May's government is to blame, according to EU negotiators.

EU negotiators have abandoned all hope that a Brexit deal will be signed with the UK at October’s European Council summit, The Independent has learned.

Brussels officials said a complete standstill in talks with Britain means securing settlements on major outstanding issues in the remaining three-and-a-half months is fanciful.

They point to the political logjam in Theresa May’s government as the obstacle blocking negotiations, piling pressure on the prime minister to break the deadlock this week.

She is set to meet her full cabinet on Friday at Chequers for a meeting that may go late into the night, in a bid to finally thrash out the government’s approach to post-Brexit relations with the EU.

The EU officials were speaking after last week’s European Council summit which saw the bloc focus on tackling immigration from north Africa, while warning Ms May that time to secure a deal is now running out.

One Brussels insider said: "There is no hope really for October now. We don’t know exactly what she is asking for yet, so how can there be?

"First the UK needs to decide what it wants, then there needs to be a discussion here and even if it is acceptable, there are processes that have to take place first before everyone agrees to move forward."

Another source close to the European Commission told The Independent: "Now we are looking at December as a more likely option, but there are questions about how much time that leaves for the deal to be ratified in time before March."

In broadcast interviews senior figures also pressed the need for urgency, with commission president Jean-Claude Juncker calling for UK negotiators to finally "make clear their positions," and Dutch prime minister Mark Rutte saying: "I am not losing patience, but time is getting shorter and shorter to come to an agreement."

Britain's Prime Minister Theresa May and European Commission President Jean-Claude Juncker hold a news conference at the EC headquarters in Brussels, Belgium December 8, 2017. REUTERS/Yves Herman Yves Herman/Reuters

On the record Downing Street is still clear that the UK’s intention is to secure a deal as quickly as possible, with October’s summit the goal.

A No 10 spokesman said when last week’s get-together concluded: "We have always been clear the Brexit is a challenging process.

"But we have made good progress so far, and are publishing a white paper next month setting out clearly what our future plans will achieve."

However, the view taken off the record by British ministers more closely corroborates the idea that the timetable has now slipped, with senior frontbenchers signalling that October has been becoming less plausible the longer the deadlock in London continues.

December is also now being seen as the moment when a deal could most plausibly be struck, something supported by the fact that the government identified 21 January 2019 as a potential staging post on the road to Brexit.

A proposed amendment to Ms May’s EU withdrawal bill, which has now received royal assent, committed a minister to making a statement to parliament if that date passes without a deal.

But if December is now the new deadline, it leaves the prime minister facing a race against time in the new year to win parliamentary backing for any agreement before Brexit takes place on 29 March 2019.

She will need to win a one-off vote backing the deal and enshrine it in a piece of legislation, which both houses of parliament may wish to amend.

Recent fraught debates and rebellions as Ms May tried to pass her EU withdrawal act have not gone unnoticed in Brussels, where officials are nervous that the prime minister may yet fail to have the deal they agree backed by enough MPs.

But first the prime minister must secure the backing of Brexiteers in her cabinet, in a crunch meeting at her official country residence that should finish with the UK being able to publish its latest Brexit white paper, setting its goals for future relations with the EU.

One potential source of friction, post-Brexit immigration rules, has been neutered for now, with government sources telling The Independent that element of Ms May’s future plans is more likely to be explored in a separate paper coming closer to September – but the vexed issue of customs arrangements still needs to be agreed by her top team.

The Chequers meeting was originally set up to start the previous day, with only those who sit on the cabinet’s Brexit subcommittee attending.

But with that group having already failed to agree to either of Ms May’s options for customs and leaning towards a harder Brexit since the departure of the more Remain-minded ex-home secretary Amber Rudd, the Thursday meeting was scrapped.

Holding a meeting of the whole cabinet could give Ms May more cover to pursue a path which would see her keep the UK in a tighter customs deal with the EU and even the single market for good.

But there has been some speculation that if she goes too far, then key Brexiteers – most notably Boris Johnson, David Davis and Liam Fox – could seize the moment and resign from her cabinet, badly destabilising her whole administration.

Those close to Mr Johnson, whose name comes up more than the others, have rubbished the idea. Either way, Downing Street insiders admit that Friday’s meeting could well be one that runs into the following day.