MPs have the power to “stop the Prime Minister in this act of madness,” the SNP Westminster leader said.

He was speaking during the debate on the UK Internal Market bill, which has split the House and caused outrage in the EU after it emerged it would break international law if implemented. 

The Tories insist it is a safety measure should the EU decide to "blockade" the movement of goods from Northern Ireland to Great Britain, but the devolved governments say it is an attempt to snatch power from them.

Ian Blackford urged the Commons: “Do not follow the Prime Minister in acquiescing in breaking the law because if you vote for second reading tonight that’s exactly what you’re all doing.”

“We have the power individually and collectively to stop the Prime Minister in this act of madness this evening.

HeraldScotland: Ian Blackford addressing the House of Commons on Monday night©UK Parliament/Jessica TaylorIan Blackford addressing the House of Commons on Monday night©UK Parliament/Jessica Taylor

“This is a matter of principle. It is about this House saying not to breach our legal obligations and I implore the House to do exactly that.”

Mr Blackford said the SNP would not support Labour’s amendment because of “some of the other conditions that are attached to it”.

The MP for Ross, Skye and Lochabar, warned that MPs had the duty to vote against the bill, adding:"This is a test for the House this evening, do not wait for the committee stage. Legally, morally, ethically, the right thing to do is to vote down this Bill tonight and this House must be accountable.

“Do not follow the Prime Minister in acquiescing in breaking the law because if you vote for second reading tonight, that’s exactly what you’re all doing. So this is a test and I understand the challenge that Conservative members face – don’t support the Prime Minister by breaking the law this evening, it is as simple as that.”

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