CALLS have flooded in for Boris Johnson to resign as Prime Minister after the UK's highest court found that he had unlawfully prorogued Parliament.

Standing outside the Supreme Court in London just after Lady Hale delivered the judge's ruling, Joanna Cherry QC the SNP MP, the lead petitioner in the Scottish legal case pursued against him, called for him to go.

"Boris Johnson should resign. His behaviour has been disgraceful and his position is untenable - if he had a shred of integrity he would jump before he is pushed," she said.

Cherry added that Parliament must be reconvened.

READ MORE: Joanna Cherry: This is a defining moment in the failure of the British state

"Parliament must resume without delay, so we can hold the Tory government to account on its Brexit plans, which threaten to plunge the UK into recession, destroy 100,000 Scottish jobs, and inflict lasting harm on living standards, public services and the economy," she said.

Scottish Greens co-convener Patrick Harvie also demanded Johnson - and his whole Cabinet - should step down immediately and that Parliament should get back to work.

"In light of the clear judgement of the supreme court that the decision to prorogue parliament was unlawful, void and of no effect it’s clear that the Prime Minister and his Cabinet must resign immediately. Their reckless actions demonstrated complete contempt for parliamentary democracy. Parliament must be recalled at once in order to hold this out of control regime to account," he said.

Nicola Sturgeon, who watched the court's ruling with her Cabinet in Bute House, Edinburgh, tweeted: "That @UKSupremeCourt judgment - upholding the Scottish Court of Session - is of truly historic proportions. The prorogation of Parliament by Boris Johnson was unlawful and of no effect. Well done to @joannaccherry@JolyonMaugham@thatginamiller."

READ MORE: LIVE: Supreme Court rules PM's suspension of Parliament is unlawful

At the Labour conference in Brighton calls rang out of “Johnson Out!” immediately after the news broke of the ruling.

The National:

In Scotland, Ian Murray, Labour MP for Edinburgh South, who was among the petitioners in the case, also called for Johnson to resign.

"This is a historic result," he said.

"The courts have upheld British democracy and delivered an astonishing rebuke to Boris Johnson for his disgraceful behaviour .

"The Prime Minister lied and politicised the Queen. He now has no option but to resign.

"It was a scandal that he suspended Parliament at the height of the biggest political crisis this country has faced since the Second World War.

"MPs must now be allowed to get back to work as early as tomorrow, and by working together we can solve this crisis by giving people a final say on Brexit - with the option to remain in the EU."

Guy Verhofstadt, chair of the European Parliament’s Brexit steering group, tweeted: “At least one big relief in the Brexit saga: the rule of law in the UK is alive & kicking. Parliaments should never be silenced in a real democracy. I never want to hear Boris Johnson or any other Brexiteer say again that the European Union is undemocratic.”