Miller insists Lords must also have vote on triggering Brexit
A fresh legal challenge to triggering Brexit could be launched unless Prime Minister Theresa May allows the House of Lords to vote on the issue.
Businesswoman Gina Miller, who helped bring the action which saw the High Court insist the Commons must vote on invoking Article 50, has said the upper House of Parliament also needs a "proper debate".
Ms Miller said that if the Supreme Court rejects the Government appeal against the High Court ruling, Mrs May should not try and bypass the Lords, according to the Daily Telegraph.
The businesswoman told the newspaper: "[There needs to be] proper debate in both houses and an act of Parliament. A resolution or a motion wouldn't be debated in both houses."
Such a move could present a major headache for Mrs May as the Government does not have a majority in the Lords.
The Supreme Court is expected to announce its Article 50 ruling early in January. Any further legal move after that could impact on Mrs May's plans to formally begin the Brexit process before the end of March.
A government spokesman said: "The country voted to leave the European Union in a referendum provided for by an Act of Parliament.”
"We are determined to respect the will of the British people and intend to trigger Article 50 by the end of March next year.
"We will respond to the Supreme Court judgment when it is delivered."