Westminster is facing unprecedented calls from the public and politicians to scrap Brexit altogether - as the Prime Minister lost control of her deadlines to leave the EU.

Theresa May has been given just three weeks to come up with a new Brexit plan if MPs do not back her withdrawal deal as public anger mounts over her handling of the negotiations.

Following lengthy talks in Brussels last night, EU leaders agreed a proposal which would delay Brexit from March 29 to May 22, on condition that MPs approve the Prime Minister’s existing agreement with the bloc.

If the deal is rejected in its third “meaningful vote” in the Commons next week, the UK would be given a deadline of April 12 to bring forward alternative proposals.

If the current or any alternative deal is not agreed by this date, Britain would have to choose between no deal or a longer extension which would mean taking part in European elections.

It came as an online petition calling for the UK’s withdrawal to be scrapped posted a record number of sign-ups, topping 2m million names this morning 

According to the Commons Petitions Committee it set new records with 2,000 signatures were being completed every minute over yesterday lunchtime, crashing the website because of the unprecedented number of those trying to sign. 

The wave of signatures comes ahead of a mass rally to take place in London over the weekend calling for a new vote, to be addressed by Scotland's First Minister Nicola Sturgeon. 

Celebrities and MPs signed up. Actor Hugh Grant wrote: “I’ve signed. And it looks like every sane person in the country is signing too. National emergency.”

SNP MP Angus Brendan MacNeil tweeted: “Next week I will, with other MPs, apply for a debate under Standing Order 24 to push for Commons vote to #RevokeArticle50.”

But No 10 said the Prime Minister had made clear failing to deliver on the Brexit result would be a failure of democracy and had “said many times she will not countenance revoking Article 50”.

In a further sign of divisions and public anger, Brexit campaigners said they plan to cause gridlock on Britain’s roads, targeting dozens of locations over the weekend.

And huge crowds are expected to turn out for a People’s Vote march in London on Saturday. 

Activity on the parliamentary website massively increased after Mrs May’s speech on Wednesday night, which caused a furious response from MPs after she blamed them for failing to implement the result of the 2016 referendum. 

She told UK  voters: “I am on your side.”

The televised message was described as being “terribly misjudged” by Nicky Morgan, the former Education Secretary, who suggested it could reduce Commons support for the PM’s plan.

It was even suggested Julian Smith, the Chief Whip, viewed the PM’s No 10 speech as “appalling”.

But Downing St defended Mrs May’s comments, saying they had been intended as a “message to the public” to explain why she had decided to seek an extension to the Article 50 withdrawal process.

There was also a suggestion – strongly rejected by No 10 – that the PM’s remarks could have endangered MPs’ safety.

Nationalist MP Pete Wishart said in the Commons: “It was the height of irresponsibility for the Prime Minister to pitch the public against Parliament in the current climate on the back of real issues of intimidation and threats against Members in all parts of the House.”

It emerged Lindsay Hoyle, the Deputy Speaker, has written to all MPs ahead of potentially crunch Brexit votes next week, recommending them to take taxis home from Parliament and not to travel alone in the coming days because of security fears.

Backbencher Anna Soubry, a leading Remainer, revealed she was unable to go home to her Nottinghamshire constituency this weekend because of the seriousness of death threats she was facing.

John Bercow, the Speaker, also intervened, telling MPs: “None of you is a traitor and all of you are doing your best…The sole duty of every Member of Parliament is to do what he or she thinks is right.”

The row emphasised the political pressure being heaped on Mrs May’s leadership.

Tory backbencher Robert Halfon, one of 20 Tory MPs to see the PM in her Commons room, said it was “a different prime minister we saw…She looked exhausted by events.”

Asked if she was going to be swept aside by them, the Harrow MP replied: “We are going to find out next week.”

The CBI and TUC took the unusual step of joining forces to warn that Britain was facing a “national emergency” and to urge the PM to change course on Brexit. 

Carolyn Fairburn, Director General of the CBI, and Frances O’Grady, the TUC General Secretary, said avoiding a no-deal was “paramount” and called for a Plan B to “protect workers, the economy and an open Irish border, commands a parliamentary majority, and is negotiable with the EU.”

In Brussels, talks overran significantly as the implications of one delay option were weighed up against another by the EU27 leaders, who had to come up with a unanimous agreement.

The session on Brexit was expected to last four hours but by early evening no conclusion had been reached and it continued over dinner, meaning that Mrs May, who was due to attend the meal, could not.

Early indications were that the EU27 was prepared to grant a short Brexit extension to May 22 and not the June 30 date Mrs May had asked for, but still conditional on her getting her deal through the Commons next week.

The PM addressed her fellow leaders for 90 minutes, the longest speech she had ever made at a European Council, but sources suggested she “did not perform well”.

When asked what she would do if she lost the parliamentary vote, Mrs May failed to answer.

According to one diplomatic source, a frustrated Emmanuel Macron, the French President, asked the PM: “Theresa, where are we going?”

After she left, EU27 leaders stayed to thrash out the options. They came to the conclusion that the PM would lose a vote next week and Britain faced crashing out of the EU without a deal on March 29.

The May 22 proposal, flagged up in the draft communique, was rowed back on as leaders discussed the implications of a no-deal Brexit. 

One option raised by France and Belgium was allowing an unconditional extension until May 7 to allow Mrs May more time to try to push a deal through Parliament.

This would have ensured the UK left before a May 9 summit in Romania to celebrate the “renewal” of Europe.

Another option on the table was an unconditional extension to April 11, the final date by which the UK could opt to take part in the May 23-26 European Parliament elections, with the possibility of a further extension if it did. 

As the summit began Mr Macron, pointed out that only a short, technical extension was on offer and if MPs rejected the agreement “it will guide everybody to a no-deal for sure”.

His remarks caused the pound to plunge by more than one per cent in its largest one-day fall this year, dropping to $1.30.

Describing the UK as being in “political crisis”, the French President, said: “There needs to be a profound political change if there is to be an extension which is anything other than technical.”

Xavier Bettel, the Luxembourg Prime Minister, said: “At the moment, there are more non-options on the table than options...I sometimes have the feeling that we are in the waiting room, a bit like Waiting for Godot. But Godot never came so I hope this time they will come.”

In other developments –
*The Ministry of Defence has set up an operations room in a bunker at its main Whitehall building to deal with a potential no-deal Brexit. The preparations are codenamed Operation Redfold.

*Jeremy Corbyn held “very constructive discussions” in Brussels with Michel Barnier, the EU chief negotiator, and Martin Selmayr, the European Commission Secretary General, which had focused on the means to prevent a no-deal Brexit next Friday.

*First Minister Nicola Sturgeon was confirmed as one of the keynote speakers at the People’s Vote Rally in London on Saturday. Other speakers will include Lord Heseltine, the former Deputy Prime Minister, Sir Vince Cable, the Liberal Democrat leader, and Labour’s Jess Philips and the Greens’ Caroline Lucas. 

*DUP MP Sir Jeffrey Donaldson said his party and other MPs still needed “legal assurances” on the Irish backstop to support Mrs May’s deal but stressed he and colleagues would “work day and night” to get those assurances. referendum.