Minister who piloted legislation for the EU referendum through Parliament admitted it was "advisory"

The commentary has been seen by some as a crucial argument for Remain campaigners in their critical Brexit legal challenge going through the Supreme Court.

Some legal experts believe Lidington's comments confirm that MPs must now still vote in order to trigger Article 50.

It is argued that a new bill to repeal the 1972 European Communities Act that took Britain into the EU must now be passed by parliament.

Lord Pannick QC, who is making the arguments on behalf of lead claimant, Gina Miller in court, has been dismissing the government’s assertion that it was entitled to use its prerogative powers to deliver notice of the UK’s intention to leave the EU under article 50 of the treaty on European Union.

Mr Lidington's crucial comments came as former First Minister Alex Salmond sought an amendment to the European Referendum Act that ensured that moves to leave the EU could only happen if there the majority of votes cast in favour in all the home nations.

Mr Lidington, then minister for Europe after rejecting the amendment said: "The legislation is about holding a vote; it makes no provision for what follows.

"The referendum is advisory, as was the case for both the 1975 referendum on Europe and the Scottish independence vote last year."

Joanna Cherry, the SNP the SNP's justice and home affairs spokeswoman in the House of Commons said Mr Lidington's comments show that MPs have to vote on the triggering of Article 50.

"Brexit cant happen without an Act of Parliament for the MPs to vote on," she said.

Constitutional expert Professor Peter Catterall of the University of Westminster believes the referendum is not legally binding.

He said: "It is possible to have a mandatory referendum, but there was nothing written into law to make the one held on June 23 mandatory. There is simply the political promise given in the Tory manifesto that the result will be respected.

"The problem with that pledge is that it is contradictory. The Tories clearly want a Brexit a la carte, just as they have always wanted an EU membership a la carte, but they cannot pick and choose what Brexit means."

He believes a defeat in the Supreme Court will mean the government will look at two pieces of legislation that will have to be voted on by MPs in Parliament, a short bill which, to give them authority to trigger Article 50 and another that will talk to the detail which he referred to as the ‘Great Repeal Bill’.

Another constitution expert, Michael Keating, professor of politicas at the University of Aberdeen said the referendum was "explicitly advisory" and he it is being treated as constitutionall binding. He said: "This is a constitutional morass and people are making up rules as they go along.

"The UK Government's main argument is that Brexit is foreign affairs and comes under the prerogative power, which is contentious because if affects domestic policy and treaties cannot be used to change domestic law."

The Government faces a wait until next year to find out whether it has won its historic Brexit legal challenge at the UK's highest court.

Eleven Supreme Court justices - a record number to hear an appeal - will announce their decision "as quickly as possible" in the new year, but no date has yet been fixed.

At the completion of four days of detailed legal argument, Lord Neuberger, president of the UK's highest court, announced: "The ultimate question in this case concerns the process by which that [EU referendum] result can lawfully be brought into effect.

"As we have heard, that question raises important constitutional issues and we will now take time to ensure the many arguments presented to us orally and in writing are given full and proper consideration."

The proceedings began on Monday amid a blaze of publicity around the world and followed a High Court ruling against the Government on November 3.

A panel of three judges, headed by Lord Chief Justice Lord Thomas, decided then that Prime Minister Theresa May lacked legal power to use the royal prerogative to trigger Article 50 of the Lisbon Treaty to start the two-year process of withdrawing from the European Union.

Opponents say an Act of Parliament is needed, but the latest Supremen Court proceedings were rounded off with a final claim by James Eadie QC, for the Government, that the use of the royal prerogative is lawful.

He said the Government is asserting that the prerogative provides "a specific power to notify Article 50 and so start the process of withdrawal notwithstanding that will result in changes to domestic law".

Mr Eadie told the court the EU Referendum Act 2015 had set up the June vote. The use of the prerogative is "consistent with the legislative scheme" to give effect to the outcome of the vote to leave the EU.

He acknowledged that if primary legislation was required to trigger Brexit, it would have to be by way of an Act of Parliament.