Reacting to the ruling, Speaker of the House of Commons John Bercow says: "I welcome the Supreme Court’s judgement that the prorogation of Parliament was unlawful.
"The judges have rejected the government’s claim that closing down Parliament for five weeks was merely standard practice to allow for a new Queen’s Speech.
"In reaching their conclusion, they have vindicated the right and duty of Parliament to meet at this crucial time to scrutinise the executive and hold ministers to account.
As the embodiment of our Parliamentary democracy, the House of Commons must convene without delay.
"To this end, I will now consult the party leaders as a matter of urgency."