The highest court in Scotland has ruled that Boris Johnson's suspension of Parliament is unlawful.
Three judges ruled that the PM's advice to the Queen was motivated by trying to "stymy" parliament and was "unlawful" and is therefore "null and of no effect."
It prompted Labour's Sir Keir Starmer to call for the PM to recall Parliament this afternoon.
He said: "I need to get back to Parliament, to see if we can reopen the doors and hold Johnson to account.
"It was obvious to everyone that shutting down Parliament at this crucial time was the wrong thing to do.
"The Prime Minister was not telling the truth about why he was doing it. The idea of shutting down Parliament offended everyone across the country, and then they felt they were not being told the truth."
The decision on appeal comes less than 36 hours after the Commons was shut down despite the ongoing legal case.
Parliament was prorogued just after 1am on Tuesday in the face of unwilling Speaker John Bercow, who warned it was being used as an act of “fiat”.
The appeal judgement appears to reverse an initial finding in the same case at Edinburgh’s Court of Session last week.
Lord Doherty said the prorogation was lawful last Wednesday morning.
But three judges of the Inner House, the supreme civil court in Scotland, disagreed with Lord Doherty's ruling.
Their judgement said the Prime Minister's advice to the Queen was "motivated by the improper purpose of stymying Parliament and it, and what has followed from it, is unlawful".
It concluded: "The Court will accordingly 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 verdict will now trigger a final hearing at the UK Supreme Court in London next Tuesday, a lawyer backing the case said.
Campaigning QC Jo Maugham added: "We believe that the effect of the decision is that Parliament is no longer prorogued."
The UK Government plans to appeal against the latest ruling.
Speaking outside court today, victorious SNP MP Joanna Cherry said she was confident the decision would now be upheld by the Supreme Court.
She branded the prorogation of Parliament “a plot to prevent us representing our constituents views” and scrutinise ministers over a back-door no-deal Brexit.
Ms Cherry was one of a cross-party group of 75 MPs and Peers who argued that the the Prime Minister's decision to prorogue Westminster to reduce the time parliamentarians have to scrutinise Brexit legislation or attempt to prevent a no-deal Brexit was unlawful.
Jolyon Maugham QC, who was second petitioner in the case, tweeted: "We have won. Appeal begins in the Supreme Court on Tuesday.
"We believe that the effect of the decision is that Parliament is no longer prorogued.
"I have never been able to contemplate the possibility that the law could be that our sovereign Parliament might be treated as an inconvenience by the Prime Minister.
"I am pleased that Scotland's highest court agrees. But ultimately, as has always been the case, it's the final arbiter's decision that matters.
"We will convene again in the Supreme Court next week."
A UK Government spokesperson 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.”
During the original hearing it was revealed that the Government appeared to consider suspending Parliament as early as mid-August, two weeks before publicly announcing the move and despite Mr Johnson's spokesman claiming at the time that any suggestion of prorogation was "entirely false".
A note dated August 15 from Nikki da Costa, a former director of legislative affairs at Number 10 - which was seen by Mr Johnson and his adviser Dominic Cummings - asked whether an approach should be made to prorogue Parliament.
The dates suggested were between September 9 and October 14.
A note of "yes" was written on the document, the Court of Session in Edinburgh heard, although the author of the annotation was not disclosed in court.
At the appeal hearing on Friday Aidan O'Neill QC, representing the parliamentarians, claimed prorogation was unlawful in his closing arguments.
He said: "A decision to prorogue shuts down Parliament. It is in those circumstances an attack on democracy.
"It is an attack on the balance of the constitution and therefore is is unlawful."
David Johnston QC, representing the UK Government, had argued it was not for the courts to get involved in what was a political decision.
Responding to the decision Tom Watson has criticised Parliament's suspension after a it was ruled unlawful at the appeal court in Edinburgh.
After being told of the ruling after his speech to the Creative Industries Federation, Labour's deputy leader said: "Whatever the legalities of it, and it does seem to me, and I hear this on the doorstep of West Bromwich, the idea that you would ask MPs to go on a month-long gardening leave... at the point when we are near the disaster of no-deal, I think people are just astounded at that.
"What they expect us to be doing is working seven days a week, Saturday and Sunday, night and day, sitting down at the table to find a compromise position that gets us out of it."
