BORIS Johnson’s job is on the line after Scotland’s highest civil court ruled he acted unlawfully by suspending Parliament for five weeks ahead of Brexit.

The Court of Session in Edinburgh said the Prime Minister was “motivated by the improper purpose of stymying” Westminster, and that he had effectively misled the Queen in advising her to prorogue Parliament.

There were gasps as the explosive ruling was read out by the Lord President, Lord Carloway, Scotland’s most senior judge, shortly after 10am yesterday. Campaigners said it was the most significant constitutional law decision of the last century.

The UK Government has appealed the decision to the UK Supreme Court for a definitive ruling, with a three-day hearing set to kick off on Tuesday next week. Mr Johnson faces being forced to recall Parliament if the Supreme Court upholds the Scottish decision. Number 10 has pledged to abide by its judgement.

READ MORE: Court of Session rules proroguing Parliament was unlawful 

However, lawyers acting for the cross-party group of more than 70 MPs and peers behind the Court of Session bid last night wrote to the UK Government and the Commons Speaker insisting its ruling meant Westminster is no longer prorogued and business must resume.

The extraordinary constitutional row came as Downing Street refused to publish internal communications relating to the decision to suspend Parliament, despite a demand from MPs.

HeraldScotland: The front page of today's edition The front page of today's edition

But in response to a motion passed in Westminster, it published its Operation Yellowhammer documents on preparations for a no-deal Brexit. The papers were previously leaked to the media.

Meanwhile, UK business minister Kwazi Kwarteng attracted criticism after telling the BBC’s Andrew Neil Show that many people were beginning to question the impartiality of judges. 

He said: “I think that they are impartial. But I’m saying that many people, many Leave voters, many people up and down the country are beginning to question the impartiality of the judges.”

Number 10 has repeatedly insisted Parliament was prorogued in order to bring forward a new legislative agenda. 

Former Tory attorney general Dominic Grieve said Mr Johnson should resign “very swiftly” if he is found to have misled the Queen over the reasons for suspending Westminster.

Speaking to the BBC, he said: “I think the judgment is a serious indictment on the Government because, leaving aside whether the ruling in law is correct, it is quite clear that on the facts, the judges in Edinburgh concluded that the Government’s explanations for proroguing Parliament were simply inaccurate and untrue.”

Mr Grieve said Parliament should be recalled “immediately” and should be sitting again within 24 hours.

He said: “If it were to be the case that the Government had misled the Queen about the reasons for suspending Parliament and the motives for it, that would be a very serious matter indeed.

“Indeed in my view, it would then be the moment for Mr Johnson to resign and very swiftly.

“Because it’s a shameful act. We operate a very good constitution in this country, and it’s based on good faith and trust from top to bottom.

READ MORE: Nicola Sturgeon hits out at Downing Street over bias claim after Court of Session ruling 

“What a minister says at the despatch box must be accurate and truthful. 

“If it’s inaccurate it must be corrected as quickly as possible.

“When the Government says it’s doing something for a particular reason, they must be able to sustain that and, if it turns out they are doing it for another reason, that is a breach of one of the fundamental tenets of how we operate.”

He added: “I think that if that were to be the case that this had happened, Boris Johnson would find himself in an untenable position in Parliament. And I hope it would be untenable not just because of the opposition, but because actually every member of the Conservative Party that believes in our constitution would simply say it’s over.”

His view was echoed by others, including Labour MP David Lammy and former Liberal Democrat leader Sir Menzies Campbell. 

Sir Ed Davey, deputy leader of the Lib Dems, also said the row could lead to Mr Johnson’s resignation. 

Mr Johnson did not directly address the court ruling as he held his second “People’s PMQs” event via a live video link on social media.

However, taking handpicked questions from the public, he rejected a suggestion he was the leader of an “authoritarian regime”. 

Dozens of MPs turned up at Westminster following yesterday’s court ruling in protest at its continued suspension. 

SNP Westminster leader Ian Blackford wrote to Mr Johnson insisting Parliament should be recalled immediately. First Minister Nicola Sturgeon said the ruling was of “huge constitutional significance”.

Gina Miller, the anti-Brexit campaigner who is pursuing a similar court case in London to stop prorogation, said Parliament should reconvene “with immediate effect”. 

A panel of three judges at the Court of Session ruled Mr Johnson’s decision to prorogue Parliament was “motivated by the improper purpose of stymying” it, and was therefore unlawful.

A cross-party group of MPs and peers, led by the SNP’s Joanna Cherry QC, had asked the court to rule the Prime Minister exceeded his powers when he asked the Queen to prorogue parliament on August 28.

They appealed to the Inner House of the Court of Session after an initial ruling from Lord Doherty rejecting their case last week. 

Lord Doherty insisted the suspension was “political territory” and could not be measured against legal standards. But yesterday, three appeal judges — including the Lord President — backed the campaigners’ case.

A summary of their ruling states that all three “decided that the PM’s advice to HM the Queen is justiciable, that it was motivated by the improper purpose of stymying Parliament and that it, and what has followed from it, is unlawful”. 

They said the court would now “make an Order declaring that the Prime Minister’s advice to HM the Queen and the prorogation which followed thereon was unlawful and is thus null and of no effect”.

The Lord President said the circumstances around the decision to prorogue Parliament, and the content of documents lodged at the court by the UK Government, demonstrated that the true reason to suspend Westminster was to “stymie parliamentary scrutiny of the executive”.

In a damning judgement, Lord Brodie said it was an “egregious case of a clear failure to comply with generally accepted standards of behaviour of public authorities”.

He said it “was to be inferred that the principal reasons for the prorogation were to prevent or impede Parliament holding the executive to account and legislating with regard to Brexit, and to allow the executive to pursue a policy of a no-deal Brexit without further parliamentary interference”, the summary stated.

Lord Drummond Young said the circumstances of the prorogation “showed that the purpose was to prevent such scrutiny”. 

The summary of his ruling added: “The documents provided showed no other explanation for this. 

“The only inference that could be drawn was that the UK Government and the Prime Minister wished to restrict Parliament.”

There was an electric atmosphere in court one of the Court of Session in Edinburgh as the ruling was read out. Outside, campaigners had gathered with placards and EU flags.

Delivering the ruling, the Lord President said: “Each opinion expresses the view that the advice given by the Government to Her Majesty the Queen to prorogue Parliament from September 9 to October 14 was unlawful, and that therefore the prorogation itself was unlawful.”

He said the court was conscious that its decision differed from that handed out by the High Court in London last week, which ruled the move to prorogue Parliament was political and not a matter for the courts.

The Lord President added: “The matter is likely, therefore, to require resolution by the UK Supreme Court.”

Following the decision, Ms Cherry called for Parliament to be recalled immediately.

She said: “Now, for every moment Parliament remains prorogued, the British Government are breaking the law. So we, as politicians, are calling for Parliament to be recalled so that we can get on with scrutinising what this Government is up to in relation to Brexit. But as a Scottish MP and a Scottish lawyer, I’m very proud that Scotland’s highest court has made this unanimous ruling.”

She added: “This is probably the most significant constitutional law decision of the last century across the jurisdictions of the United Kingdom, and it will have major repercussions.”

A UK Government spokesman said: “We are disappointed by today’s decision, and will appeal to the UK Supreme Court. The UK Government needs to bring forward a strong domestic legislative agenda. Proroguing Parliament is the legal and necessary way of delivering this.”

Parliament’s prorogation began in the early hours of Tuesday amid chaotic scenes in the Commons. 

Downing Street has made clear MPs will not be immediately recalled following the Court of Session ruling. The Supreme Court’s three-day hearing is due to consider appeals from Scotland, the High Court in London and a similar legal action in Northern Ireland. Ms Miller said its judgment is not likely to be delivered until the week of September 23.