A cross-party group of politicians has launched legal action attempting to stop Boris Johnson forcing through a no-deal Brexit by suspending Parliament.
The crowdfunded challenge is being led by the Good Law Project, the same team that won a victory at the European Court of Justice last year over whether the UK could unilaterally cancel Brexit by revoking Article 50.
Shutting down Parliament - known as proroguing - to prevent MPs being able to vote against leaving the EU without a deal is "unlawful and unconstitutional", according to the challenge backed by more than 70 MPs and peers.
The Prime Minister has threatened to take the UK out of the EU with or without a deal by October 31.
With the UK Government and the EU seemingly at a standoff over renegotiating the thrice-rejected Withdrawal Agreement, Mr Johnson has not ruled out proroguing Parliament to force no-deal Brexit through.
A group of politicians including Liberal Democrats leader Jo Swinson, Labour MP Jess Phillips and SNP MP Joanna Cherry have asked the Court of Session in Scotland to declare that Prime Minister Boris Johnson cannot lawfully advise the Queen to close down Parliament.
Founder of the Good Law Project Jolyon Maugham QC said: "The fact that so many MPs elected by the people are going to the Court of Session to stop a Prime Minister selected by members of the Conservative Party from suspending Parliament tells you quite how profoundly our politics has declined."
The legal papers, lodged with the Court of Session in Scotland as it sits through the summer, states: "Seeking to use the power to prorogue Parliament to avoid further parliamentary participation in the withdrawal of the UK from the EU is both unlawful and unconstitutional."
Warning that "the exercise of the power of prorogation would have irreversible legal, constitutional and practical implications for the United Kingdom", the challenge calls for the court to declare that proroguing Parliament before October 31 would be both unconstitutional and unlawful by denying MPs and Lords the chance to debate and approve the decision.
While no date has been set to hear the case, the campaigners have stressed the time-sensitive nature of the challenge, with less than three months until the current withdrawal date.
The challenge adds: "The issues raised in this petition clearly concern a live constitutional issue on which there is a real and practical necessity to have the court's determination as a matter of urgency."
