The Government is to appeal against a High Court ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union.

Campaigners were celebrating victory in the legal battle against Theresa May's decision to use the royal prerogative in her Brexit strategy, with demands for her to now set out her negotiating strategy to MPs.

In one of the most important constitutional cases in generations, three senior judges ruled that the Prime Minister does not have power to use the prerogative to trigger Article 50 of the Lisbon Treaty to start the two-year process of negotiating Brexit without the prior authority of Parliament.


Within minutes of the ruling by Lord Chief Justice Lord Thomas, International Development Secretary Liam Fox told the House of Commons that the Government will appeal to the Supreme Court.

And a Government spokesman said: "The Government is disappointed by the Court's judgment. The country voted to leave the European Union in a referendum approved by Act of Parliament. And the Government is determined to respect the result of the referendum.

"We will appeal this judgment."

Unless overturned on appeal at the Supreme Court - or at a potential further appeal to the European Court of Justice in Luxembourg - the ruling threatens to plunge the Government's plans for Brexit into disarray as the process will have to be subject to full parliamentary control.

Dr Fox told the Commons that the Government was "disappointed" at the High Court ruling, but remained "determined to respect the result of the referendum".

"There will be numerous opportunities for the House to examine and discuss what the Government is negotiating," said the International Trade Secretary - a leading Brexiteer.

"When we are clear about the position we will adopt then Article 50 will be triggered but given the nature of the judgment this morning we will now have to await the Government's appeal to the Supreme Court."

Labour leader Jeremy Corbyn said: "This ruling underlines the need for the Government to bring its negotiating terms to Parliament without delay.

"Labour respects the decision of the British people to leave the European Union. But there must be transparency and accountability to parliament on the terms of Brexit. Labour will be pressing the case for a Brexit that works for Britain, putting jobs, living standards and the economy first."

The ruling was welcomed by opponents of a "hard Brexit".

Liberal Democrat leader Tim Farron said the Government must now lay out its negotiating position in Parliament, while Scottish First Minister Nicola Sturgeon described the finding as "significant indeed". Green co-leader Caroline Lucas hailed it as "brilliant news", adding: "That's what taking back control should be about - better democracy."

But Ukip leader Nigel Farage said he feared that "a betrayal may now be near at hand", warning he had "a distinct feeling" that the political classes "do not accept the June 23 referendum result".

"I now fear that every attempt will be made to block or delay the triggering of Article 50," said Mr Farage. "If this is so, they have no idea of the level of public anger they will provoke."

Government lawyers had argued that prerogative powers were a legitimate way to give effect "to the will of the people" who voted by a clear majority to leave the European Union in the June referendum.

But Lord Thomas declared: "The Government does not have power under the Crown's prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union."

The Lord Chief Justice - sitting with the Master of the Rolls, Sir Terence Etherton, and Lord Justice Sales - emphasised to a packed court that he was deciding "a pure question of law".

He added: "The court is not concerned with and does not express any view about the merits of leaving the European Union: that is a political issue."

Prime Minister Theresa May announced at the Conservative Party conference that she intends giving an Article 50 notification by the end of March 2017.

Her opponents were "concerned citizens" drawn from all walks of life, with the lead challenge brought by investment fund manager and philanthropist Gina Miller.

Outside the Royal Courts of Justice Ms Miller was greeted by rounds of applause. Ms Miller said the result was "about our United Kingdom and all out futures. It's not about how anyone voted. Every one of us voted for the best country and the best future."

The Supreme Court is understood to have set aside time in early December to hear the Government's appeal, Mrs May's official spokeswoman told a Westminster media briefing.

A minister will spell out the Government's position in a statement to Parliament on Monday. Mrs May will not deliver the statement herself, as she will be away on a long-planned trip to India.

"Our plans remain to invoke Article 50 by the end of March," said the PM's spokeswoman. "We believe the legal timetable should allow for that."