Article 50: Government must consult MPs before triggering Brexit, court rules

The decision means that the Prime Minister cannot trigger Article 50 of the Lisbon Treaty, which starts the formal discussions on Brexit, without parliamentary approval.

Parliament will likely now be given greater powers of scrutiny over EU negotiations, and that Article 50 could be delayed past Theresa May's planned trigger date of March 2017.

MORE: Updates on the fallout from the court ruling

Mrs May had argued that the referendum result and ministerial powers meant that MPs do not need to vote, but opponents argue this is unconstitutional.

The government says it will appeal the decision to the Supreme Court.

Wolverhampton South East MP Pat McFadden has welcomed the ruling, but said he did not think that Parliament would consider blocking the triggering of Article 50.

"This is not about Parliament overturning the result of the referendum," added Mr McFadden, who sits on the Brexit select committee.

"It is a case of MPs having a say on the terms on which we leave the EU."

A three day hearing at the High Court last month looked at whether, as a matter of UK constitutional law, the government is entitled to give notice of a decision to leave the EU by exercise of the Crown's prerogative powers and without reference to Parliament.

It was brought by investment manager Gina Miller, who said she was 'absolutely delighted' with the court's decision. Her case was supported by a Polish national from Wolverhampton, who said she was concerned about her right to stay in the UK.

The UK voted for Brexit in June's referendum by a margin of 51.9 per cent to 48.1 per cent.

The EU's other 27 members have said negotiations about the terms of the UK's exit - due to last two years - cannot begin until Article 50 has been invoked.