UP to one million people are expected to attend a People’s Vote march and rally in London today as the continuing political turbulence at Westminster threatens not only Theresa May’s Brexit plan but also her premiership.

With voters from the four corners of the country descending on the UK capital to demand a second chance to vote on Britain’s future, Nicola Sturgeon insisted this was now the “moment of maximum opportunity” to avoid the twin catastrophes of the Prime Minister’s deal and a no-deal.

“The EU’s decision to postpone things until at least April 12 has opened a window and those of us who oppose Brexit must seize the chance it offers,” declared the First Minister.

She said that next week the House of Commons must seize control from the failing Conservative administration to secure a longer extension to the Brexit process to allow time for a new referendum to be held.

“The Prime Minister and her Government have proved completely incapable of delivering on the result of the 2016 vote, which is why it is right that this should now go back to the people,” insisted Ms Sturgeon.

She added: “Scotland voted overwhelmingly to remain in Europe and has been completely ignored by the UK Government throughout the Brexit process. That has demolished Tory claims that the UK is a partnership of equals and is making the case for independence stronger than it has ever been.

“But whatever Scotland’s future - and I hope and believe it will be an independent one - it is in all of our interests for UK to be in the EU,” she added.

Labour’s Tom Watson, who will also be on today’s Put It to the People march, pledged to vote for Mrs May's twice-rejected Brexit deal to prevent the UK crashing out of the EU but only if she vowed to let the public have a say on it.

He will tell the rally that he has reluctantly come to the view that the only way to resolve the current impasse is "for people themselves to sign it off".

Labour supports a second referendum as one possible option but has not formally said it would back the PM's deal on the condition it was put to a public vote.

Mr Watson will tell the crowds in Westminster that Brexit is “stuck in the pipework of Parliament” with MPs deadlocked.

“The current impasse is not working for people who voted to leave or people who voted to stay. I really don't think Parliament will be able to resolve this,” the party’s deputy leader will declare.

"That's why I've come to the reluctant view that the only way to resolve this and have legitimacy in the eyes of the public is for the people themselves to sign it off. It can only bring closure if we're all involved in making the decision,” he will add.

The organisers say “several dozen” MPs from all the main parties will attend the rally, which will be addressed by, among others, Tory peer Lord Heseltine, the former Deputy Prime Minister, Sir Vince Cable, the Liberal Democrat leader, and Labour’s Sadiq Khan, the London Mayor.

Meanwhile, the Commons online petition to scrap Article 50 and keep Britain in the EU topped 3.6 million signatures by yesterday evening, adding 2.5m in less than 24 hours following the PM’s appeal to voters to back her in her stand-off with MPs.

Mrs May has made clear: "I do not believe that we should be revoking Article 50."

But Patrick Harvie, the co-convener of the Scottish Greens, who will also be at today’s rally in Parliament Square, welcomed the “phenomenal support” for the record-breaking petition, which, he said, showed the strength of feeling people had about ending the Brexit chaos.

“Scotland has repeatedly called for the narrow 2016 result and the Remain vote here to be respected but we have been ignored at every turn by an utterly blinkered Prime Minister.

“The country still risks being driven off the edge of a cliff but it’s not too late for Parliament to stop that by putting the final decision back to the people or, if all else fails, use the powers, which Green MSPs helped secure through the courts and revoke Article 50 in the public interest,” added the Glasgow MSP.

Labour’s Ian Murray, a prominent Remainer, added: “This is a march to stop the madness of Brexit. The last 1,000 days have destroyed trust in politics and time is now running out to avoid a catastrophic no-deal exit from the EU.

“This national crisis can only be resolved by putting the decision back to the British public,” added the Edinburgh MP.