In a verdict upholding a High Court decision, the UK’s most senior court this morning dismissed the Government’s appeal against last November’s verdict.
By a mjority of eight to three, Supreme Court judges ruled the Government must gain an Act of Parliament before triggering Article 50.
But the Supreme Court boosted the Government by ruling devolved parliaments in Scotland, Wales and Northern Ireland do not need to vote on Article 50 before Brexit can begin.
The verdict represents a major blow to Scottish First Minister Nicola Sturgeon's fight against her country being taken out of the EU.
Attorney-General Jeremy Wright, who presented the Government's case during the Supreme Court hearing last month, said: "Of course the Government is disappointed with the outcome.
"The Government will comply with the judgement and do all that is necessary."
Mr Wright added the Supreme Court had been clear "it has not been deciding whether the UK should or should not leave the EU".
He said: "The people of the UK have already made that decision", adding Brexit is now a "political mater and not a legal matter".
Theresa May must get the consent of MPs before triggering Article 50
The Liberal Democrats and SNP have already stated their MPs will try to defeat an Article 50 bill
Today's ruling means the Prime Minister now has 67 days to secure the consent of Parliament before invoking Article 50 and beginning EU divorce talks.
Mrs May has repeatedly vowed to trigger Article 50 by the end of March and had hoped to avoid a parliamentary showdown over Brexit by insisting ‘royal prerogative’ powers gave her the right to trigger Article 50 alone.
The Supreme Court today agreed with the High Court the Prime Minister does not have that power.
The Government is already believed to have drafted a short parliamentary bill aimed at authorising Brexit negotiations, which MPs could now vote on as early as next week.
Brexit Secretary David Davis will address the House of Commons later today.
Lord Neuberger reads out the Supreme Court decision
Fears MPs could try and derail Brexit through a vote on Article 50 have been eased after Labour leader Jeremy Corbyn insisted his party would not block Britain’s EU departure.
But it has been reported up to 80 Labour MPs, including some shadow cabinet members, could defy their party leader and vote against Article 50.
The Liberal Democrats and SNP have already stated their MPs will try to defeat an Article 50 bill.
Opposition parties are also likely to try and add amendments to the bill in an attempt to meddle with Brexit negotiations.
House of Commons clerks have told Labour they will not be able to add amendments relating to specific aspects of Article 50 talks, such as forcing the Government to ensure continued access to the Single Market as part of any Brexit deal.
But they could demand the Prime Minister officially publishes her Brexit negotiating aims and force a parliamentary vote on any exit deal early enough so the Government could be sent back to Brussels to negotiate a new one.
A spokesperson for Mr Corbyn said: “Labour respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50.
“However, Labour will seek to amend the Article 50 Bill to prevent the Conservatives using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe.
“Labour will seek to build in the principles of full, tariff-free access to the single market and maintenance of workers' rights and social and environmental protections.
“Labour is demanding a plan from the Government to ensure it is accountable to Parliament throughout the negotiations and a meaningful vote to ensure the final deal is given Parliamentary approval."
Meet the Supreme Court Judges who will get last say on Article 50
Thu, December 1, 2016
These are the Supreme Court Judges who could stop Theresa May triggering Article 50 next week, throwing the UK’s plans to break from the EU into total disarray.
1 of 12
The Supreme Court Judges.
Meanwhile, despite previous threats from peers they could delay or even block the approval of Article 50, the House of Lords is also expected to authorise the start of Brexit talks.
The Government has already put peers on notice it could revive efforts to curb the powers of the House of Lords if it hampers Brexit.
Tory MPs have also suggested swamping the House of Lords with hundreds of Brexit-backing peers should it vote against Article 50, while there have also been calls to scrap the upper chamber completely if it defies the EU referendum result.
More to follow…