Shane Clarke, a senior director at Tourism Ireland, told the Northern Ireland Affairs Committee on Wednesday new authorisation requirements proposed under Britain’s Nationality & Borders Bill will likely discourage tourists from heading north.
"A lot of visitors can be spontaneous in terms of what they decide to do when they come. You may well have an independent traveller who has originally planned to come to Dublin and then, for example, they hear about the Game of Thrones attraction in Banbridge and they want to go up there so you get a lot of activity.
"Similarly you get people who will want to go up to Donegal. They would really need to transit through Northern Ireland in order to get there. Introducing this kind of regulation is going to be quite inhibitive," he said.
Under the proposed legislation the UK's Immigration Act 1971 will be amended and non-Irish European Union and non-EU citizens - including those permanently resident in the 26 counties - will have to apply for and pay for an electronic travel authorisation (ETA) to get into the six counties.
Dr. Joanne Stuart, Chief Executive Officer of the NI Tourism Alliance told the committee this could have all sorts of implications. She said people could easily end up crossing the border without an ETA quite innocently.
"We do have a connected health system and people could find themselves in that situation without even realising it. And also the single entry is the real challenge with this in that people who do decide to travel across the border - whether it's for leisure or medical or some other reason - will find themselves breaking the law without maybe realising it," said Dr. Stuart.
Mr. Clarke said it would put tour operators off coming to the north.
"People would be less likely to travel into Northern Ireland. Tour operators would be less willing to programme it because of the complexities associated with it and the costs associated with it because you wouldn't want your coach driver to be breaking the law inadvertently in anyway.
"Northern Ireland is also a transit point for people going from the south of Ireland up to Donegal so again there is all that complexity."