Britain's Supreme Court has ruled that the Parliament must vote on whether the government can start the Brexit process on Tuesday, according to BBC reports.

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A pro-Europe supporter shows off products whose names have been changed as he waits outside the Supreme Court, before the decision of a court ruling on whether Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London, Britain, January 24, 2017.??[Photo/Agencies]

The ruling means Theresa May cannot begin talks with the EU until MPs and peers give their backing - although this is expected to happen in time for the government's 31 March deadline.

But the court ruled the Scottish Parliament and Welsh and Northern Ireland assemblies did not need a say.

Campaigners argued denying the UK Parliament a vote was undemocratic.

But the government said it already had the powers to trigger Article 50 of the Lisbon Treaty - getting talks under way - without the need for consulting MPs and peers.

The judges rejected the case put by ministers by a majority of eight to three.

Attorney General Jeremy Wright said the government was "disappointed" but would "comply" and do "all that is necessary" to implement the court's judgment.