A legal challenge to try to prevent Boris Johnson shutting down parliament to force through a no-deal Brexit has begun in a Scottish court.
A group of MPs and peers wants the Court of Session in Edinburgh to rule that suspending parliament to make the UK leave the EU without a deal is "unlawful and unconstitutional".
The prime minister has repeatedly refused to rule out such a move.
Lord Doherty agreed to hear arguments from both sides in September.
However he refused to accelerate the case through the Scottish courts, with the petitioners voicing fears that they may run out of time before the UK is due to leave the EU on 31 October.
The start of the legal action came as it emerged the UK government expects a group of MPs to try to block a no-deal Brexit by attempting to pass legislation when Parliament returns next month.
A No 10 source said they expected the challenge to come in the second week of September, when MPs are due to debate a report on Northern Ireland.
The source assumes the EU will wait until after that date before engaging in further negotiations.
More than 70 politicians have put their names behind the move, including Lib Dem leader Jo Swinson and SNP MP Joanna Cherry.
A challenge brought by the same group of anti-Brexit politicians last year saw the European Court of Justice rule the UK can cancel Brexit without the permission of the other 27 EU members.
Jolyon Maugham QC, director of the Good Law Project which is supporting the latest challenge, said: "A man with no mandate seeks to cancel parliament for fear it will stop him inflicting on an unwilling public an outcome they did not vote for and do not want.
"That's certainly not democracy and I expect our courts to say it's not the law."
The UK is currently due to leave the EU on 31 October, with the prime minister pledging that Brexit will definitely happen on that day regardless of whether or not a deal has been agreed with the EU.
Most MPs at Westminster are opposed to a no-deal Brexit, and there has been speculation that Mr Johnson could try to get around this by closing parliament in the run-up to 31 October.
This is known as proroguing, and would require the permission of the Queen.
Mr Johnson argued during the Conservative leadership contest that he would not "take anything off the table", saying it would be "absolutely bizarre" for the UK to "weaken its own position" in negotiations with European leaders.
But the group of pro-Remain politicians involved in the legal action at Scotland's highest court argue that shutting down parliament in this manner would be unlawful.
The case is beginning in the Scottish courts because they sit through the summer, unlike their English counterparts.
During a procedural hearing in Edinburgh, lawyers argued that the case could ultimately be decided in the UK Supreme Court - but only after it has moved through the Scottish system.
Lord Doherty refused a motion from the petitioners to skip the first step of this, saying arguments must be heard in the outer house of the Court of Session before they proceed to the next stage, the inner house.
However he did agree to move swiftly, fixing a full hearing for 6 September.
'Can't go unchallenged'
The Commons Speaker John Bercow has said the idea of the parliamentary session ending in order to force through a no-deal Brexit is "simply not going to happen" and that that was "so blindingly obvious it almost doesn't need to be stated".
One of the petitioners, Edinburgh South Labour MP Ian Murray, said: "When Boris Johnson unveiled his vacuous slogan 'taking back control', voters weren't told that this could mean shutting down parliament.
"The prime minister's undemocratic proposal to hold Westminster in contempt simply can't go unchallenged."