The Government resisted an amendment that could have made the EU referendum legally binding, the leading lawyer in the case against Article 50 has said.

Lord Pannick QC, who represents Gina Miller in the case against the Government’s plans to trigger Article 50 without a vote by MPs, made the claims while addressing the Supreme Court today.

He said: “The 2015 [EU Referendum] Act said nothing whatsoever about the consequences of the referendum.

“If Parliament meant the 2015 Act to have legal effect, it could and it would have done so. The Government resisted an amendment to give legal force to the referendum.”

The 2015 Act was established under then-Prime Minister David Cameron and set out the terms of the EU referendum, which was subsequently heard in June.

The terms of the Act have been scrutinised by judges since, amid concerns it did not provide enough clarity or direction on whether the referendum was legally binding.

Eleven of Britain’s most senior judges are hearing arguments in the Supreme Court appeal after the High Court ruled against Theresa May’s Brexit plans. They are considering whether Ms May has the authority to do so alone, or must get parliamentary approval through a vote by MPs.

The Government’s lawyers have argued Ms May is entitled to do so due to her powers as Prime Minister and head of the executive.

Supreme Court Brexit Challenge Show all 13 1 /13 Supreme Court Brexit Challenge Supreme Court Brexit Challenge People wait to enter the public gallery outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Gina Miller, co-founder of investment fund SCM Private arrives at the Supreme court in London on the first day of a four-day hearing Getty Supreme Court Brexit Challenge A man waves the EU flag in front of the Supreme Court Getty Supreme Court Brexit Challenge Satirical artist Kaya Mar poses with two of his paintings in front of the Supreme Court Getty Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin. The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge Businesswoman Gina Miller arrives at the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin Getty Supreme Court Brexit Challenge Attorney General Jeremy Wright arrives at the Supreme Court in London EPA Supreme Court Brexit Challenge Protesters outside the Supreme Court in London, where the Government is appealing against a ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union PA wire Supreme Court Brexit Challenge A protesters wearing a judge's wigs and robes stands outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge A protester holds up a placard outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court Getty Supreme Court Brexit Challenge A man waiting to enter the public gallery waves a European Union flag outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters

They have suggested the “average man or woman on the street” would think the referendum entitled her to do so. They have also warned that if the Supreme Court upholds the High Court’s decision, it could have wider reaching implications; including limiting the Government's power in international affairs by requiring them to seek parliamentary approval more often.

The case is expected to last four days, concluding on Thursday.