UK-registered cars will need to display a GB sticker in the Republic of Ireland after Brexit, the government has said.
New government advice said the sticker must be displayed in any EU country.
Motorists from the UK driving in the Republic are currently advised to display the sticker, but the rule is not widely enforced.
The advice applies to cars registered in all parts of the UK, including Northern Ireland.
The sticker, a white oval containing the letters GB, standing for Great Britain, must be displayed at the rear of the vehicle.
Northern Ireland is not a part of Great Britain – which is made up of England, Scotland and Wales – but the GB sticker is used for cars from all parts of the UK.
The rule will apply to drivers even if their number plate includes a GB logo.
Sinn Féin MP for West Belfast, Paul Maskey, said he would not be displaying one of the stickers on his car.
Many nationalists in Northern Ireland, identify as Irish rather than British, raised objections on social media to being required to have a GB sticker.
Seamus Leheny of the Freight Transport Association criticised the advice as “frivolous”.