THOUSANDS of protesters will today call for a general election as UK ministers become increasingly resigned to delaying Britain’s exit from the EU due to the backlog of Brexit bills at Westminster.

A rally in London’s Trafalgar Square, organised by the People’s Assembly Against Austerity, has drawn inspiration from the Gilets Jaunes movement in France and will feature speeches from a raft of politicians, union leaders and campaigners demanding a snap poll.

Steve Turner of Unite, the trade union, said the Conservative Government was “fixated on ideological austerity that, like their Brexit strategy, has divided our nations and failed to deliver an economy that works for anyone other than a growing rich elite”.

As tension mounts ahead of Tuesday’s crunch Brexit vote, suggestions have been made that Theresa May could be looking at a defeat on a massive scale with a majority as high as 200 against her Brexit Plan.

However, one Whitehall insider made clear that even if MPs rejected the Prime Minister’s proposal, this would not be the end of the matter.

He told The Herald: “If the deal is voted down, that does not kill the deal. The deal remains the best option.”

The senior insider explained that if the May Plan were rejected, then MPs would in the following days realise that there was “no magical smorgasbord of Brexit options” and that it would be quickly resubmitted for a second vote.

Earlier this week, David Mundell, the Scottish Secretary, made a similar suggestion that if the May Plan were voted down, a period of reflection would help “crystallise” in MPs’ minds that the alternatives were no-deal or no Brexit and both of these would be totally unacceptable.

If, as expected, the PM’s proposal is rejected, then Mrs May must return by Monday week to disclose what her Plan B is.

It is thought that within a matter of days MPs would debate and vote on this second proposal, which, crucially, John Bercow, the Commons Speaker, will announce is amendable. This would mean, for example, MPs voting to extend the Article 50 process and push back exit day from March 29.

Jeremy Hunt, the Foreign Secretary, warned of “Brexit paralysis” that could lead to Britain remaining in the EU should Mrs May’s Plan be rejected.

He also said Parliament was “very committed” to stopping a no-deal outcome, noting: “We have seen from this week that Parliament has the ability to assert itself and to shape outcomes.”

Senior ministers increasingly believe the sheer scale of legislation that still needs to be processed before March 29 means an extension is inevitable.

One said: “The legislative timetable is now very, very tight indeed. Certainly, if there was defeat on Tuesday and it took some time before it got resolved, it’s hard to see how we can get all the legislation through by March 29.”

At present, in addition to legislation that will be needed for the final deal itself, MPs have to pass a Fisheries Bill, an Immigration Bill, a Trade Bill, an Agriculture Bill, a Health Care Bill and a Financial Services Bill. It is believed that even if MPs sat over weekends and Westminster’s February recess were cancelled, they would not have time to process all the necessary legislation.

However, No 10 continued to insist: “We will ensure either way[deal or no deal] we will have passed the necessary legislation and we will make sure the time is made available."

Last night, John McDonnell, the Shadow Chancellor, said: "Extending Article 50 has to be on the table if Parliament can't agree on the process forward or if it's so late in doing that."

Earlier at a pro-People’s Vote “emergency convention” in London, Dominic Grieve, the former Attorney General, whose successful amendment means the PM has to reveal her Plan B within three days instead of 21, also insisted the Article 50 process now had to be extended to allow a second referendum to take place.

In between standing ovations, the Buckinghamshire MP declared: "Parliamentarians do have some duties and one of them is to prevent people from committing national suicide."

This weekend, the PM is expected to have telephone talks with more trade union and business leaders as well as with some EU counterparts.

On Monday, Brussels is due to reveal its “further assurances” on the Irish backstop. Jean-Claude Juncker, the European Commission President, said the EU27 had been in “constant” touch with Downing St.

He said: “We will see what the British legislature decides to do with the texts that have been put forward. I still hope there will be a deal. I do not like the prospect of a no-deal, which would be a disaster for our British friends and for the continent of Europeans.”

Mr Juncker added: “Every effort needs to be made between now and Tuesday afternoon perhaps to ensure this important issue can be resolved satisfactorily.”

Elsewhere, Scotland Yard revealed that, in line with similar advice at a national level, it was advising retailers to consider “planning for additional security” amid fears that public concern over potential shortages of food and other goods in the event of a no-deal Brexit could lead to a “significant increase in customers”.