Drivers from Northern Ireland may need a special "green card" when travelling to the Republic, insurers have warned.
The Association of British Insurers (ABI) has said that drivers will need a green card if they wish to drive in countries which are part of the European Union following a no-deal Brexit.
There are approximately 110 million border crossings between Northern Ireland and the Republic each year, the Department for the Economy has said.
A Green Card is an internationally recognised insurance document which provides proof of the minimum compulsory motor insurance cover required by the country visited.
The cards provide a guarantee of insurance for a minimum of 15 days and can remain valid until the expiry date of the motor insurance policy, providing cover for multiple trips.
Currently all motor vehicles with a valid registration travelling within the EU are covered by the terms of the EU Motor Insurance Directive (MID).
The green card will not be needed if an agreement is reached between the EU and UK on Brexit, or if a transitional arrangement is implemented.
A no-deal Brexit is looking increasingly likely, with the UK set to leave the EU on March 29, with no deal currently in place.
Prime Minister Theresa May's withdrawal deal was overwhelmingly defeated on Tuesday.
The ABI has warned drivers to contact their insurer at least a month before they wish to travel to obtain a green card for proof of insurance. It would likely cost a "small administrative charge".
Anyone planning to take their vehicle to mainland Europe, and freight companies planning to transport goods will also need the green card after March 29. Those travelling without them may be breaking the law.
An agreement was reached between European insurance authorities in May 2018 to waive the need for Green Cards in the event of a no-deal Brexit, however this has not yet been confirmed by the European Commission.
Director General of ABI Huw Evans urged drivers in Northern Ireland to plan ahead.
“If you live in Northern Ireland and drive to the Republic of Ireland, or if you plan to drive your vehicle to mainland Europe after a no-deal Brexit, you will need a Green Card to prove you are insured," he said.
"You should contact your insurer before you travel in order to get one. This advice applies to businesses as well as individuals.
“It remains the case that Insurers do not want a ‘no deal’ Brexit; it would be bad for the economy and bad for our customers. We continue to hope these arrangements are never needed and urge the Government, UK Parliament and EU27 to agree an orderly way forward.”