Raymond McCord, a prominent victims rights campaigner whose son was killed by loyalist paramilitaries in 1997, lodged an application for judicial review at the High Court in Belfast last week.

His first application for legal aid was turned down, but the decision was overturned on appeal yesterday.

Mr McCord’s application for a judicial review will be heard at a leave hearing tomorrow.

He will argue that withdrawal from the EU would contradict the UK’s international obligations under the Good Friday Agreement, and any notification under Article 50 would also require a mandate from MPs.

Mr McCord’s solicitor, Ciaran O’Hare of McIvor Farrell Solicitors, has said the application “is an important constitutional case which engages the Northern Irish public interest in a way that no other case has or is likely to for many decades”.