THE SNP leadership has signalled it will engage in guerrilla tactics at Westminster to "frustrate" Theresa May’s Government as another constitutional clash between Edinburgh and London looms on the forthcoming Brexit Trade Bill.

After leading a mass walk-out of Nationalist MPs in the Commons – branded a “stunt” by opponents - their leader Ian Blackford suggested his party would use a number of “parliamentary devices” to disrupt UK Government business and to highlight what the SNP believes is the Conservatives’ "anti-Scottish" agenda. “We will take them on,” he declared.

First Minister Nicola Sturgeon, who made clear she was “right behind” her colleagues at Westminster, accusing the UK Government of treating Scotland with “contempt,” suggested that it could no longer be business as usual between Edinburgh and London. Planned meetings between the two governments could now be cancelled.

SNP sources have made clear to The Herald that the Scottish Parliament is on another collision course with Whitehall over the forthcoming Brexit Trade Bill, which is due to return to the Commons for debate next month.

Like the EU Withdrawal Bill, the UK Government has made clear it will seek MSPs’ consent on the Trade Bill as it involves devolved competencies but like the EU Withdrawal Bill it looks set to be refused it.

Stewart Hosie, the SNP’s trade spokesman, explained: “Whether it’s a power-grab or a failure to respect the will of the Scottish Parliament, we are dealing with the same issues with the Trade Bill and the same concerns will arise.

“As things stand, I can’t see how the Scottish Parliament could pass a Legislative Consent Motion to allow the Trade Bill to go forward,” added the former party’s deputy leader.

In a day of high drama at Westminster, Mr Blackford clashed with John Bercow, the Commons Speaker, after the UK Government for the first time pressed ahead with legislation affecting Scotland, the Brexit Bill, in the face of opposition from Holyrood.

During a rowdy Prime Minister’s Questions, the SNP leader decried how the Conservative Government had “plunged Scotland into a constitutional crisis” by what he regarded as a breach of constitutional convention; that Holyrood’s approval on devolved matters should be sought and received.

He used a parliamentary device by calling for an immediate vote on turning PMQs into a private session, which would have barred the public and press, but the Speaker refused and ordered him to leave the chamber. Amid bitter barracking, Mr Blackford did so followed by all of his SNP colleagues.

Outside, he explained relations between the SNP and the Conservative Government had broken down and were in crisis.

Explaining his party’s future strategy, he said: “We will be robust in using parliamentary devices to make sure we can hold this Government to account…and frustrate what it is seeking to do.”

The Nationalists, he said, would use Commons procedures to oppose Government in every conceivable way and have an impact on its business on a “day to day and week by week basis”.

“We are in a situation that the Westminster Government has shown utter disrespect to the Scottish Parliament and the people of Scotland by wilfully ignoring that the Scottish Parliament has refused to give a consent motion.

“They are now acting outwith the support of the Scottish people. The Conservatives have returned to where they were before in acting in a manner that is anti-Scottish. We are not having it,” declared the MP for Ross, Skye and Lochaber.

His deputy, Kirsty Blackman, called on David Mundell to “stand down - and stand down now” as he had “utterly failed to protect devolution”.

But the Scottish Secretary said the SNP had “put a stunt over substance,” which underlined how the party had sought to “use Brexit as a cover to change the constitutional settlement to give the Scottish Parliament a veto over UKwide responsibilities; something we cannot accept”.

He acknowledged the lack of debate on Scottish concerns about the Brexit legislation was “not a good optic” but suggested Labour’s unnecessary votes ate up valuable time that could have been used for debate.

Mr Mundell added that the UK Government was “committed” to continuing to work with the Scottish Government and seek the consent of Holyrood in relation to common frameworks that flowed from the bill.

Following the wave of indignation expressed by SNP and Labour MPs over the lack of debating time for Scottish issues on Tuesday night, it emerged that a paper left on the Commons green benches suggested subsequent Nationalist Points of Order had been choreographed as it referred to what questions should be asked and how SNP MPs should show "outrage/disappointment".

It was also suggested the Speaker was minded to grant the Nationalists a so-called SO24 debate, probably today, but that Mr Blackford’s actions and his party’s mass walkout had killed the idea.

Instead, Mr Mundell will make a Commons statement on the issue of devolution and the Brexit Bill this afternoon, enabling MPs to have their say on the issue.

Elsewhere, Paul Sweeney, the Shadow Scotland Office Minister, denounced the SNP’s “absurd stunt,” which would only appeal to the party’s “zealots,” and illustrated how desperate the Nationalists were becoming.

Noting how five SNP MPs had questions down for Mrs May but were unable to ask them because they had walked out, the Glasgow MP said: “I’m sure their constituents were rather disappointed those MPs were not able to raise their concerns in Parliament on this critical issue for the people of Scotland.”

Christine Jardine, the Liberal Democrats’ spokeswoman on Scotland, also denounced the Nationalists’ “stunt” and said it meant the opportunity to have a Scottish SO24 debate had been lost.

The Edinburgh MP added that it suited both the SNP and the Tories to “crank up” the constitutional issue rather than focus on the bread and butter issues, which concerned voters, like jobs and the cost of living.

Last night, Nationalist sources claimed such was the indignation felt at the Tory Government’s treatment of the Scottish Parliament’s opposition to the Brexit Bill and the lack of opportunity for Scottish MPs to debate the issue, some 1,000 people had applied to join the party.