Proceedings began on Monday at the UK's highest court as the British government attempts to overturn a ruling that Parliament must hold a vote before Britain's European Union exit negotiations can begin.

Prime Minister Theresa May plans to trigger two years of divorce talks before the end of March by invoking Article 50 of the EU's key treaty, using centuries-old government powers known as royal prerogative.

The powers - traditionally held by the monarch but now used by politicians - enable decisions about joining or leaving international treaties to be made without a parliamentary vote.

Financial entrepreneur Gina Miller and hairdresser Deir Dos Santos went to court to argue that leaving the EU will remove some of their rights, including free movement within the bloc, and that shouldn't be done without Parliament's approval.

Last month, three High Court judges agreed.

But the government says they have misinterpreted the law.

Government lawyers led by Attorney General Jeremy Wright will argue this week that the British people have spoken by voting in a June 23 referendum to leave the EU.

They say a parliamentary vote would mean getting lawmakers "to answer precisely the same question which was put by Parliament to the electorate and has been answered in the referendum."

Many legal experts say the government will likely lose its appeal and be forced to give Parliament a vote.

In a reflection of the constitutional importance of the case - which hinges on the balance of power between Parliament and the executive - all 11 Supreme Court judges will hear the appeal, the first time the full court has sat since it was founded in 2009.

The case is scheduled to last four days, with a ruling likely in January.

UK POOL

London - 5 December 2016

1. Zoom in from man waving European Union flag outside court building to flag

2. Attorney General for England and Wales Jeremy Wright arriving with his associates

3. Protest bus passing outside court, people on it chanting UPSOUND (English) "Nigel, where are you!"

4. Gina Miller, investment fund manager and philanthropist who was one of the team that won the High Court ruling, arriving with her associates, posing for photographers in front of court entrance

Opposition leader Jeremy Corbyn has welcomed Tuesday's Supreme Court ruling that UK parliament should be consulted before the government triggers Article 50 to leave the European Union.

The Labour party leader said he would not block the government's plan to invoke Article 50 by the end of March, saying "it doesn't mean we abdicate the field, it means we then hold the government to account".

UK POOL

London - 24 January 2017

1. SOUNDBITE (English) Jeremy Corbyn, British opposition Labour party leader:

"We will support Article 50 being triggered, we have made that very, very clear. That is the result of the referendum and we have to respect that. It doesn't mean we abdicate the field, it means we have to hold the government to account on the issues of trade, the issues of rights and the issues of the long-term direction in which this country wants to go. Because the strange thing about the Prime Minister's speech was this implied threat that if Europe doesn't do what she wants, then she's going to turn us into some Singapore-style economy on the shores of Europe. Well, that is not what people voted for, people voted for leaving the European Union, they didn't vote to vote themselves out of work."

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2. SOUNDBITE (English) Jeremy Corbyn, British opposition Labour party leader:

"I think it's quite appalling that the government has not produced a White Paper as a statement of what its intents are. All we have is a speech that the Prime Minister made at Lancaster House, we've got the court judgement this morning and we're going to have a statement apparently from David Davis (UK Brexit Secretary) a bit later on today in the House. Frankly, there should be a proper statement of what the government intends to do on this. We have been making the point ever since the referendum that parliament must be involved. We must be able to hold the government to account, that's what parliament exists for, to hold them to account to make sure that the negotiations actually are for the benefit of all the people of this country, however they voted in the referendum."

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3. SOUNDBITE (English) Jeremy Corbyn, British opposition Labour party leader:

"I don't think it's good enough. We cannot say, okay, Article 50, you go off and negotiate and in two year's time you come back with a vote. That's not acceptable. We need to be informed, be able to challenge, be able to overturn if necessary, the objectives and direction in which the government is going on those negotiations. There is also going to be the Great Repeal Bill which will come up presumably during the coming summer. That's going to be an enormous piece of legislation because it is amending 40 years of UK parliamentary legislation, all of which at some point or the other usually refers to European regulations. But we're very clear; we're going to hold them to account. We're going to hold them to account to protect jobs, we're going to hold them to account to make sure British industry does have market access and we're not going to allow ourselves to become some kind of off-shore tax haven. That's not what people voted for."

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4. SOUNDBITE (English) Jeremy Corbyn, British opposition Labour party leader:

"Look every MP represents a constituency, every MP has people that voted either way in the referendum. Every MP represents a constituency and people are worried. They're worried about jobs, they're worried about services, they're worried about rights. There's a whole sense that we will succeed in uniting people around the objectives of the kind of decent, inclusive, caring society we want in Britain. We don't want to become a haven for funny money and dodgy tax avoiders."

++ENDS ON SOUNDBITE++