John McDonnell has brushed aside SNP calls for Labour to call a no-confidence vote in Theresa May’s Government, suggesting Nicola Sturgeon knows it would fail and with it the chance of a general election in which the Nationalists would lose seats to his party in Scotland.

In remarks that will infuriate the First Minister, the Shadow Chancellor said: “The SNP have got their own motivation, which is to try and avoid a general election.

“Who can delve into the mind of Nicola Sturgeon but my view is that they want to lose a vote of no-confidence and then avoid a general election because they know we're breathing down their necks in Scotland; we'll take seats off them in so many marginals."

He added: "They're terrified of a general election. They're sitting on a large number of marginal seats at the moment and we'll take them."

But the SNP hit back with a spokesman saying: "John McDonnell is clutching at straws; the SNP would relish a general election.

"We are the only party which has been consistent in its opposition to the Tories' Brexit shambles and recent polls suggest we would win seats from Labour, not the reverse.

"However, this is not the time for game-playing or finding excuses to do nothing; it is a time for clear and decisive leadership."

Earlier Ms Sturgeon appealed to Jeremy Corbyn to call a snap no-confidence vote, saying: "If the time is not right now, when will the time be right?"

The Herald understands the Labour leader has cancelled a meeting with Ian Blackford, the Nationalist leader at Westminster, due for this afternoon in light of the inter-party spat, which will do little to help co-operation between them on coalescing on an alternative to the Prime Minister’s Brexit Plan.

Earlier, Mr Corbyn was given until tonight by other opposition leaders to table a no-confidence vote in the Tory Government or they would seek to take the initiative themselves tomorrow.

Mr Blackford urged the Labour leader to accept his responsibility to call a no-confidence vote and if he did not, then the other opposition parties would move to table one.

However, parliamentary convention is that the sitting government allows time for the official Opposition to table a no-confidence motion because it is a potential administration; the same does not apply to a third party like the SNP.

Claiming the PM’s decision to pull the Brexit vote was “an act of cowardice,” the Nationalist Leader at Westminster said: “If Jeremy, for whatever reason, does not do that, then I as the leader of the third party will accept my responsibility and give that signal to the Government that we have no confidence in them.

“I’m suggesting Jeremy has to do that by the close of business tonight, then we have to look at the earliest opportunity to do that…Possibly tomorrow.”

The Highland MP, speaking after a People’s Vote press conference under the slogan “If not now, when?” and involving senior representatives of all the main parties, added: “There has to be a vote of no-confidence at the earliest opportunity. Given where we are it would be better if there was one this week.”

During an emergency debate in the Commons, Mr Blackford’s SNP colleague Pete Wishart urged Mr Corbyn “to do the right thing” by tabling a motion of no-confidence so the country could be “shot of” the Tory Government.

But the Labour leader replied: “We have no confidence in this government. We need to do the appropriate thing at the appropriate time to have a motion of no-confidence to get rid of this government.”

At the People’s Vote press conference, Sir Vince Cable, the Liberal Democrat leader, claimed Mr Corbyn had “a duty” to call a no-confidence vote and offer the official Opposition as an alternative administration given the Tory Government was collapsing and panicking.

He said the chances of a People’s Vote was “quite high” but denied this would raise the prospect of a second referendum on Scottish independence, saying they were totally different issues. “This has nothing to do with Scottish independence,” he declared.

Asked if a People’s Vote to remain in the EU would lead to social unrest, the Lib Dem leader said: “No. Jeremy Hunt the other day was warning about riots; this is inflammatory stuff. I don’t think the British public are going to riot.”

He admitted there was anger on all sides but suggested that if the Government pressed ahead with Brexit, then the country would be “disgruntled for years and decades to come” but a People’s Vote would be as good a way to find of removing people’s anger.

Sir Vince confirmed that he and Mr Blackford could seek to table a no-confidence vote in the Government tomorrow if Mr Corbyn failed to do so. “It could happen tomorrow,” he told The Herald.

The cross-party group called for not only Mr Corbyn to table a no-confidence vote but also on the Government to make the necessary legislative preparations to enable a People’s Vote and on EU leaders to allow for an extension of the Article 50 timetable to free up more time to facilitate a second vote.

Dame Margaret Beckett, the former Foreign Secretary, also called on her party leader to “think very hard about adding your signature to those of the other leaders here today, table a motion of no -confidence so that, if you cannot get the General Election we want, you can campaign for the People’s Vote that Labour’s members and voters so desperately desire”.

Tory Remainer Anna Soubry, who made clear she would vote with her Government in any motion of no-confidence, pointed out that this would nonetheless then clear the way for a bid for a People’s Vote.

“The concern for someone like me is frankly that Jeremy Corbyn is prevaricating. He is giving every reason why we can’t have a People’s Vote and we want him to get on with it.”

Asked about the threat of social unrest and possible violence on the streets, as some have suggested, if a People’s Vote overturned the 2016 referendum result, Ms Soubry replied: “That’s disgraceful. What a grossly irresponsible thing to say. That’s putting up scare stories to frighten people.”

The Nottinghamshire MP added: “Look, 52 per cent of my constituents voted Leave, so that was the situation in 2016. Yes, it’s been a hugely divisive issue. That division exists and it will only deepen if there is a sense there’s been some sort of conspiracy between the two frontbenches to deny people a right to a final say now we know what Brexit looks like.”

However, the cross-party calls for Mr Corbyn to call a snap no-confidence vote did not wash with the Labour leadership.

Ian Lavery, the party’s Chairman, tweeted: “The SNP and others calling for an immediate no-confidence vote admit that they know it would fail.

“They know a failed motion would unite the Tories, prevent us from getting a general election, and keep this shambles of a Tory Government in power.

“Labour’s policy, as democratically decided by our members at Conference, is to bring about a general election so we can do away with this disastrous Government that’s botching Brexit and running our country into the ground. That is our priority, as agreed by our members.

“Theresa May has lost all authority. We are fully prepared to bring a no-confidence motion for the purpose of defeating the Government and forcing a general election. But we aren’t going to table one for the purpose of it being defeated, strengthening May and uniting Tories.”