THE Government has lost an historic battle in the Supreme Court over Brexit.

This morning, by a majority of eight to three, judges at the Supreme Court rejected the Government's argument that Theresa May could use prerogative powers to trigger the talks under Article 50 of the EU treaties, but must first seek Parliament's approval.

This means the process of Britain leaving the European Union cannot formally begin until MPs have voted in the Commons.

The judgement was made 'owing to the well-established rule that prerogative powers may not extend to acts which result in a change to UK domestic law'.

Downing Street said the Government's defeat will not derail the PM's plan to start negotiations on withdrawal from the EU by the end of March.

Ministers are now expected to publish a short bill authorising the invocation of Article 50, with votes to take place in the Houses of Commons and Lords soon.

Attorney General Jeremy Wright - who led the Government's legal fight - said ministers were "disappointed" by the ruling, but added: "The Government will comply with the judgment of the court and do all that is necessary to implement it."

A Downing Street spokesman 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 six to one 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."

The Supreme Court judges ruled against an argument that Mrs May must also consult devolved administrations in Scotland, Wales and Northern Ireland before triggering Article 50. 

There was relief in Downing Street over the decision on devolved administrations, which could have been much more significant in upsetting Mrs May's timetable if it had gone the other way.

Labour leader Jeremy Corbyn said his party would not "frustrate the process for invoking Article 50" but would seek to amend the legislation to prevent the UK becoming a "bargain basement tax haven".

"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," said Mr Corbyn.

The SNP, the third largest party in the Commons, said it will put forward 50 "serious and substantive" amendments to the legislation.

Gina Miller, the lead claimant in the Brexit challenge, welcomed the Supreme Court's ruling, saying "no prime minister, no government can expect to be unanswerable or unchallenged.

"Parliament alone is sovereign."

Outside the central London court, she said that MPs will now have the chance to help the Government select the "best course" in Brexit talks.

She also spoke of how this "divisive issue of a generation" had led to her and her legal team facing "extraordinary and unwarranted criticism".

Ms Miller said: "Today, eight of the 11 Supreme judges upheld the judgment handed down by the High Court in November in a case that went to the very heart of our constitution and how we are governed.

"Only Parliament can grant rights to the British people and only Parliament can take them away.

"No prime minister, no government can expect to be unanswerable or unchallenged. Parliament alone is sovereign.

"This ruling today means that MPs we have elected will rightfully have the opportunity to bring their invaluable experience and expertise to bear in helping the Government select the best course in the forthcoming Brexit negotiations - negotiations that will frame our place in the world and all our destinies to come.

"There is no doubt that Brexit is the most divisive issue of a generation but this case was about the legal process, not politics."

"In Britain we are lucky, we are fortunate to have the ability to voice legitimate concerns and views as part of a shared society.

"I have therefore been shocked by the levels of personal abuse that I have received from many quarters over the last seven months for simply bringing and asking a legitimate question."

She added: "I sincerely hope that going forward that people who stand in positions of power and profile are much quicker in condemning those who cross the lines of common decency and mutual respect."

David Greene, the lawyer for the other claimant, pro-Brexit hairdresser Deir Dos Santos, said: "The court has decided that the rights attaching to our membership of the European Union were given by Parliament and can only be taken away by Parliament.

"This is a victory for democracy and the rule of law. We should all welcome it."

South Swindon MP Robert Buckland said: "At the Referendum, people around the country and within our Swindon community backed different sides, but the result of the vote was clear. It is now the job of the government to deliver on that decision and to take this great moment of national change to build a stronger, fairer, more secure and prosperous Britain.

The Wiltshire Gazette and Herald:

South Swindon MP Robert Buckland

"The Supreme Court's decision meant that they rejected the Government's argument about the way in which the Article 50 process is to be started. I am very proud that we live in a country where respect for the Rule of Law and the independence of our judiciary is paramount.

"As a Law Officer, my duty is to help uphold these principles. Whilst vigorous debate as to the legal merits of the judgment is part of our democracy, unjustified and personalised attacks on judges diminish us all."

Julie Girling, Conservative MEP for the South West and Gibraltar, said today: "It is no secret I supported the 'remain' campaign. However this judgement is not about whether you are for or against EU membership; it is about the procedural requirements necessary before starting the Brexit process.

"It is important that our Houses of Parliament play a central role in these complex negotiations, in order to ensure the UK gets the best possible deal. Trade with the EU accounts for around half of both UK exports and imports in goods and services.

"The referendum simply showed a majority of voters wanted to leave the EU - the procedural requirements and the terms of a future relationship have never been put to a vote.

"I am convinced that a hard Brexit would be hugely detrimental to the UK and therefore believe it is key for our elected representatives to remain central to the discussions. Parliamentary sovereignty is a cornerstone of our constitution and must be respected."

Lord Chancellor Liz Truss delivered a staunch defence of the judiciary in the wake of the Government's Supreme Court defeat on Brexit.

In a statement issued minutes after the judgment was handed down, she described the justices as "people of integrity and impartiality".

Last year Ms Truss came under fire over claims she had not spoken out quickly enough in defence of three High Court judges. They had faced fierce criticism after ruling Parliament must be given a vote on triggering Brexit negotiations.

Responding to the Supreme Court judgment today, Ms Truss said: "Our independent judiciary is the cornerstone of the rule of law and is vital to our constitution and our freedoms.

"The reputation of our judiciary is unrivalled the world over, and our Supreme Court justices are people of integrity and impartiality.

"While we may not always agree with judgments, it is a fundamental part of any thriving democracy that legal process is followed. The Government has been clear that it will respect the decision of the court."

Ms Truss had come under pressure to speak out publicly when a furore erupted following the High Court judgment in November.

The judges were branded "enemies of the people" by one newspaper and faced criticism from some politicians.

Legislation will be introduced "within days" to ensure the Government can stick to its timetable of triggering the process of leaving the European Union by the end of March,

Brexit Secretary David Davis told MPs that legislation will be introduced "within days" to ensure the Government can stick to its timetable of triggering the process of leaving the European Union by the end of March,

Mr Davis said the Government's defeat in the Supreme Court would not derail Theresa May's timetable to kick off the two-year process of withdrawal negotiations.

He said the Supreme Court ruling did not affect the fact Britain will be leaving the EU in line with the result of the 2016 referendum, telling MPs: "There can be no turning back.

"The point of no return was passed on June 23 last year."