BORIS Johnson should resign “very swiftly” if he is found to have misled the Queen over the reasons for suspending Parliament, a former Tory attorney general has said.

Dominic Grieve made the comments after Scotland’s highest civil court ruled the Prime Minister’s decision to prorogue Westminster was unlawful.

There were gasps when the decision was read out at the Court of Session in Edinburgh, and the UK Government is now appealing to the Supreme Court.

Speaking to BBC News, Mr Grieve 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."

READ MORE: Court of Session rules proroguing Parliament was unlawful 

He added: "We have been making the same point in the House of Commons."

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

He added: "It wasn't to reset the Government and have a suspension of Parliament for a short time followed by a Queen's speech. It was to prevent us holding the Government to account.

"So, I would hope that the Government would now realise the extent of the crisis it has created and recall Parliament immediately."

He added: "It would be much more sensible that the Government should simply say we are dropping the Supreme Court case's appeals on both sides, Parliament will sit, and arrange for us to sit in the next 24 hours."

The MP for Beaconsfield, who had the Tory whip removed earlier this month over his support for legislation aimed at preventing a no-deal Brexit, said it was “absolutely essential to our constitution that the relationship between the Prime Minister and the Queen is one of the utmost confidentiality and utmost good faith”.

He added: “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, my view is 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, but it’s based on good faith and trust top to bottom.

“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.

READ MORE: The Court of Session's damning statement on Boris Johnson's 'unlawful' decision 

“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."

A panel of three judges at the Court of Session said they 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".

A cross-party group of more than 70 MPs and peers led by SNP MP Joanna Cherry QC had asked the court to rule Mr Johnson exceeded his powers when he asked the Queen to prorogue parliament on August 28.

They appealed to the court's Inner House after Lord Doherty initially insisted the move was "political territory" and could not be measured against legal standards.

A summary of the Court of Session ruling states that all three judges "have 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".