Speaking in the Assembly yesterday, Dr Caoimhe Archibald, MLA for East Londonderry, said the provision, included in the landmark Nationality and Borders Bill, would “create unreasonable levels of bureaucracy and unacceptable legal uncertainty for thousands of citizens”.

She added that the reliance on “ad-hoc in-country checks” as opposed to checks at the border could “create a real risk of racial profiling”, and the measures would “harden the border for thousands of our fellow EU citizens”.

Under the bill, non-Irish EU citizens crossing the border without pre-travel clearance could face penalties of fines or up to six months’ imprisonment.

Dr Archibald concluded: “The proposal needs to be scrapped. There is also an onus on the Irish government and the EU to make it clear to the British government how fundamentally unworkable and unacceptable it would be.”

The Nationality and Borders Bill has completed its journey through the House of Commons and is now at second reading in the House of Lords.