Boris Johnson’s decision to suspend Parliament was unlawful, the Supreme Court has ruled.
Mr Johnson suspended – or prorogued – Parliament for five weeks earlier this month, saying it was to allow a Queen’s Speech to outline his new policies.
But the court said it was wrong to stop Parliament carrying out its duties in the run-up to the Brexit deadline.
The court’s president, Lady Hale, said: “The effect on the fundamentals of our democracy was extreme.”
She said the unanimous decision of the 11 justices was that Parliament had not been prorogued – the decision was null and of no effect – and it was for the Speakers of the Commons and Lords to decide what to do next.
Commons Speaker John Bercow welcomed the ruling and said Parliament “must convene without delay”, adding that he would now consult party leaders “as a matter of urgency”.
BBC home affairs correspondent Dominic Casciani said the ruling was “the worst outcome for the prime minister”.