THERESA May today warned Brussels there won't be a Brexit deal unless they ditch plans to carve off Northern Ireland from the rest of the UK.

Speaking in the Commons, the PM said that Britain and the EU are now "not far apart" on the key question of the Irish border.

She vowed to hold firm against Brussels' bid to impose new customs controls between Northern Ireland and mainland Britain - claiming the plan is ILLEGAL.

But the PM was accused of seeking a "Hotel California Brexit" after she refused to confirm the date that Britain will quit the European customs union.

Mrs May told MPs: "We are entering the final stages of these negotiations.

"This is the time for cool calm heads to prevail - and it's the time for a clear-eyed focus on the few remaining but critical issues that are still to be agreed.

"We have made real progress in recent weeks on both the withdrawal agreement and the political declaration on our future relationship.

"The shape of a deal across the vast majority of the withdrawal agreement - the terms of our exit - are now clear.

"Perhaps most significantly, we have made progress on Northern Ireland, where the EU have been working with us to respond to the very real concerns we had on their original proposals."

Mrs May confirmed plans for a temporary "backstop" keeping Britain in the customs union as a way of avoiding a hard border in Ireland - although she repeatedly refused to name the date when that arrangement would come to an end.

Brexiteers including Boris Johnson and Iain Duncan Smith tried to press the PM on the point but she would only say that she "expects" the backstop to finish in 2021 at the latest.

Labour's Alex Sobel blasted: "I didn't realise the Prime Minister was an Eagles plan - she has put the country into Hotel California, where we can check out any time we like but we can never leave."

Mrs May revealed that the EU has been seeking a so-called "backstop to the backstop" - which would put Northern Ireland in a different customs territory to the rest of the UK.

The PM warned Eurocrats must ditch their plans to impose a border between Britain and Northern Ireland, saying: "Creating any form of customs border between Northern Ireland and the rest of the UK would mean a fundamental change in the day-to-day experience for businesses in Northern Ireland – with the potential to affect jobs and investment.

"We have been clear that we cannot agree to anything that threatens the integrity of our United Kingdom."

The PM vowed that the backstop, which will effectively keep the UK in the EU customs union until a full trade deal is agreed, would be in place no longer than 2021 and would be reversible at any time.

She concluded: "We cannot let this disagreement derail the prospects of a good deal and leave us with the No Deal outcome that no one wants.

"I continue to believe that a negotiated deal is the best outcome for the UK and for the European Union.

"I continue to believe that such a deal is achievable. And that is the spirit in which I will continue to work with our European partners."

Responding to the statement, Labour leader Jeremy Corbyn said: "This really is beginning to feel like groundhog day. Another 'nothing has changed' moment from this shambles of a Government."

Mrs May hit back, saying the leftie boss "wants to frustrate the people’s vote and frustrate Brexit".

Boris also took a pop at Mr Corbyn, saying: "The Leader of the Opposition is guilty of a shameless U-turn and a betrayal of millions of people who voted Leave."

Officials have been scrambling to cut a deal with Brussels ahead of a summit this week - but last night No10 announced that talks had been called off for now because the two sides can't agree on the crucial question of the Irish border.

On another day of Brexit drama today:

EU bosses warned a No Deal outcome is "more likely than ever"
Tory MPs publicly clashed as a senior minister accused Boris Johnson of acting like a child
Theresa May's DUP allies predicted that No Deal is now the most likely outcome
Downing Street officials launched a new charm offensive to win over Brexiteers
Pro-Brexit Cabinet ministers prepared for a "pizza summit" where they will plot a joint approach
Labour compared the PM to Neville Chamberlain, notorious for appeasing Hitler
EU leaders hinted Mrs May could be banned from attending a special Brexit summit next month

British and EU civil servants yesterday managed to thrash out a withdrawal and transition deal which could be signed off at this week's meeting of European leaders.

But when Brexit Secretary Dominic Raab rushed to Brussels for a meeting with Michel Barnier, he warned that Mrs May can't sign off on any agreement tying the UK to the EU's customs union for good or dividing Northern Ireland from Britain.

It now appears unlikely that the two sides will come up with a deal in time for this week's European Council summit which starts on Wednesday.

Council president Donald Tusk wrote in a letter to EU leaders that No Deal is now "more likely than ever before".

But he added: "The fact that we are preparing for a No Deal scenario must not, under any circumstances, lead us away from making every effort to reach the best agreement possible, for all sides.

"This is what our state of mind should be at this stage. As someone rightly said, 'It always seems impossible until it's done.' Let us not give up."

Senior British ministers insisted it won't be a problem if there is no agreement this week - suggesting that a deal could be struck at a special summit likely to take place in November.

Foreign Secretary Jeremy Hunt said this morning: "This is obviously a difficult period... but we should remember that a huge amount of progress has been made.

"There are one or two very difficult outstanding issues but I think we can get there.

"Whether we do that this week or not, who knows - but I know everyone has been trying incredibly hard."

Spain's foreign minister Josep Borrell added: "In Europe, agreements never come before the end of the time. We don't have to dramatise, we still have time. We still have one month."

Claire Perry, the Climate Change Minister who sits in the Cabinet, praised the PM's efforts - telling Sky News: "I'm very confident that she will come back with a deal.

"It might not be this month, we've got this timing thing that we've put into our heads - but we will get a deal and she's the right person to get it."

She also hit out at Boris Johnson after the top Brexiteer urged Mrs May to "stand up to bullies" by driving a hard bargain with Brussels.

Ms Perry said he was using "playground language" and added: "This is a time for incredibly serious grown-ups to be around the negotiating table."

Civil servants have reportedly told ministers that in the absence of an agreement, they should begin enacting emergency No Deal plans by the end of the month.

The contingency plans are designed to ensure that planes can still fly and goods can still cross the Channel even if we leave the EU in March without a deal.

The PM is being warned that she may not be allowed to attend next month's Brexit summit if the two sides are on course for a No Deal scenario.

Irish ambassador Adrian O'Neill said last night: "If at this week’s European Council meeting there isn’t some way forward, well then I think we will probably see people could decide to avail of the opportunity for the November meeting to focus on preparations for a No Deal outcome."

His prime minister Leo Varadkar said that even if a deal does come together it might not be until December - two months later than previously planned.

Pro-Brexit ministers are worried that Mrs May will end up agreeing to keep the UK in the European customs union for good - or even split up the country by agreeing to controls on goods travelling from Britain to Northern Ireland.

They are meeting for pizza this evening and could discuss whether or not some should quit in protest at the PM's direction of travel on Brexit.

Officials from No10 are planning to host dinner for Brexiteer backbenchers over the coming days in a last-ditch bid to persuade them to back the Chequers plan.

But ex-minister Steve Baker, shop steward of the Eurosceptic Tories, suggested the breakdown in talks was "theatre" designed to scare MPs away from No Deal.

The DUP, which is propping up Mrs May's Commons majority, is furious at the prospect of a deal which splits up the UK.

MP Sammy Wilson said: "It is probably inevitable that we will end up with a No Deal scenario."

And a party source insisted the DUP will apply maximum pressure to the Government, telling Politico: "We are going to squeeze their balls until their ears bleed."

Labour's John McDonnell predicted Mrs May will end up with a Brexit deal - but only by rolling over to Europe like 1930s PM Neville Chamberlain.

He told the Financial Times: "I think our European partners will provide sufficient fudge for May to come back.

"I think there’ll be a Neville Chamberlain moment, peace in our time. After that what will happen will be trench warfare within her own party for a considerable period of time."