Mounted by a group of unionist politicians, it argues that the protocol, part of the UK government’s Brexit deal with the EU, is contrary to the Act of Union and the Northern Ireland Act.

Its arguments were previously rejected by the High Court and the Court of Appeal. The Supreme Court will hear the case over two days.

The protocol was intended to ensure the continuance of free trade across the Irish land border in the wake of Brexit.

Traditional Unionist Voice (TUV) leader Jim Allister has led the application made to the Supreme Court.

In a joint statement with Baroness Hoey and Ben Habib, Mr Allister said they were looking for “definitive determinations as to the breach of Article 6 of the Acts of Union which the protocol inflicts and the consequences thereof, including what protection, if any, the Belfast Agreement affords against such constitutional change”.

“Ultimately, the protocol requires political defeat,” they added.

The UK government is still engaging in talks with the EU about modifications to the protocol. The case will be heard at the Supreme court today and tomorrow.