Britain's government must get parliamentary approval before starting the process of leaving the European Union, the Supreme Court ruled on Tuesday, potentially delaying Prime Minister Theresa May's plans to trigger exit negotiations by the end of March.

The 8-3 ruling from the judges forces the government to put a bill before Parliament, giving pro-EU politicians a chance to soften the terms of Brexit - Britain's exit from the EU.

"Leave" campaigners had objected, saying Parliament shouldn't have the power to overrule the electorate, which voted to leave the bloc in a June 23 referendum.

The Supreme Court's decision doesn't mean that Britain will remain in the EU - but it could delay the process.

Still, May's Brexit secretary, David Davis, told the House of Commons on Tuesday that the government timetable remained on track, and that officials would introduce a bill within days.

"They (parliament) need to be involved before we leave," said Charlie Mullins, founder of Pimlico Plumbers, who helped fund Article 50 legal challenge.

May had argued the referendum gave her a mandate to take Britain out of the EU and that discussing the details of her strategy with Parliament would weaken the government's negotiating position.

UKIP leader Paul Nuttall said the result was what he expected, saying "I think we've lost the battle today and I'm disappointed but not surprised, but we will win the war."

London - 24 January 2017

1. Pan down UK Supreme Court entrance

2. Police outside

3. Top shot media and entrance

4. Set up of Charlie Mullins, founder of Pimlico Plumbers

5. Close up Mullins' tie

6. SOUNDBITE (English) Charlie Mullins, founder of Pimlico Plumbers, helped fund Article 50 legal challenge:

"Well I think it was all unnecessary. If she would have got parliament involved, rather than you know, saying that she's gonna get on with it, then she was saying, 'oh, they can vote on this once she's negotiated a deal' - well that's all too late then. Once she's negotiated a deal, once we've left the EU and we're offered the deal we've got, there is no point in parliament getting involved. They need to be involved before we leave. And now I think they can put enough pressure on to her to make sure we get a soft Brexit."

7. Pan down Supreme Court

8. Various pro-EU demonstrators

9. Various exteriors of UK parliament

10. Various cutaways of Paul Nuttall, UK Independence Party leader

11. SOUNDBITE (English) Paul Nuttall, UKIP leader:

"I think it's what we expected, I think we've lost the battle today and I'm disappointed but not surprised, but we will win the war. And now these guys behind me in the House of Commons and the House of Lords have a duty to enact the will of the people and I want to make it clear what that will is. People voted on mass on June 23rd to leave the European Union. They also voted the leave the single market. The Prime Minister of the day, David Cameron, the Chancellor, the Foreign Secretary of the day, Philip Hammond, they all made it clear, leaving the EU means leaving the single market. The British people went out and did that by a score of 52 percent. So leaving must mean leaving."

12. Mid of Parliament

13. Various set ups Andrew Blick, Director History and Policy organisation and Lecturer King's College London

14. SOUNDBITE (English) Andrew Blick, Director History and Policy and Lecturer King's College London:

"The courts upholding that principal is a very important constitutional moment that no doubt will appear in all the textbooks for years to come. No question about the constitutional significance. The political significance is a bit more complicated. What political difference will it really make? It seems unlikely that the Commons, the House of Commons, the elected chamber of parliament, would want to be seen to be blocking Brexit, to be seen to be resisting the will of the people as expressed in a referendum. That seems very unlikely. There is perhaps an outside chance that the House of Lords, the unelected chamber, might offer some kind of resistance to the bill."

15. Cutaway

16. SOUNDBITE (English) Andrew Blick, Director History and Policy and Lecturer King's College London:

"I think that timetable (set out by British Prime Minister Theresa May) still looks very plausible, but the consequence of this judgment today is that the matter is slightly out of her (May) hands in that now she has to get statutory authorisation, she has to take a bill through parliament, she has to follow through those parliamentary procedures. It can be done quickly but it does require both Houses of Parliament to agree to it if she wants it happen quickly, so there is a slight variable in there, that wasn't in there before."

17. Various exteriors of Parliament