The Supreme Court has this morning ruled that the government cannot trigger Brexit without an act of Parliament.
The court had been asked to overturn a High Court ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union.
However, in a majority ruling of 8 to 3, the Supreme Court judges dismissed the appeal and ruled that 'an Act of Parliament is required to authorise ministers to give Notice of the decision of the UK to withdraw from the European Union.'
What happens next?
Prime Minister Theresa May could now take the case to the European Court of Justice in Luxembourg but she has already said she wants to trigger Article 50 by the end of March.
This means the UK is expected to have left the European Union by the summer of 2019.
Legislation of some form will now have to be prepared for MPs and Lords to vote upon.
A government spokesperson said: "The British people voted to leave the EU, and the government will deliver on their verdict – triggering Article 50, as planned, by the end of March. Today’s ruling does nothing to change that.
"It’s important to remember that Parliament backed the referendum by a margin of 6 to 1 and has already indicated its support for getting on with the process of exit to the timetable we have set out.
"We respect the Supreme Court’s decision, and will set out our next steps to Parliament shortly."
And Scott Knowles, Chief Executive at East Midlands Chamber, said: “The decision by the Supreme Court could have two significant impacts on business. It could delay the triggering of Article 50, which would create further doubt and uncertainty for business, and it could cause further fluctuations in the value of Sterling.
“It is essential that Prime Minister Theresa May acts immediately to assuage any doubts that could harm UK plc and reassure business that she will meet her previously stated goal of triggering Article 50 by the end of March so that business continues to have a fixed timetable for Brexit.”