SCM founder Gina Miller is to challenge Prime Minister Theresa May's right to trigger Article 50 without a vote in Parliament at the High Court today.
Miller is leading a group of campaigners who are contesting the government's authority to proceed with Brexit without asking Parliament, arguing the principle of parliamentary sovereignty underpins the constitution and the rule of law in the country, the BBC reports.
Ministers argue they can act under ancient powers of royal prerogative.
But according to Sky News lawyers for Miller will argue the Government cannot trigger the mechanism for leaving the EU using powers which for centuries were vested in the monarchy.
Miller told the publication: "We have a parliament that is sovereign. We have a functioning democracy.
"Are we now saying that we can go back to 19th-century, 18th-century politics where governments can overrule parliaments and take away people's rights, which will happen when we leave the EU.
"For me that is a very dangerous place to go."
The UK decided to leave the EU in a referendum on 23 June by a margin of 51.9% to 48.1%.
There have been growing calls from MPs on all sides of the House for the UK's Brexit negotiations to be subject to far greater parliamentary scrutiny.
While the government has not ruled out giving MPs a vote on the final settlement reached with the EU, it has said it will not countenance a vote on the timing of Article 50 or its negotiating strategy.
The case will be heard over three days at the High Court, but any appeal will be fast-tracked to the Supreme Court to be heard before the end of the year.
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