Tourism leaders have warned that UK government proposals to require international travellers to apply for a permit to cross the Irish border will damage the industry.
They were announced last year as part of the Nationality and Borders Bill.
It would require non-British and non-Irish EU citizens to apply for pre-travel clearance.
The NI Affairs Committee was told most international visitors to Northern Ireland arrive via Dublin airport.
The new Electronic Travel Authorisation (ETA) will be required for those international tourists who want to travel onwards to Northern Ireland, even if it is just for a day trip.
The system would be similar to the declaration that international passengers have to fill in before travelling to the United States or Canada.
Tourism Ireland said tour operators were "incredulous" when the plan was explained to them.
John McGrillen, chief executive of Tourism NI, said one of the major concerns was that travel agents and tour operators would cut Northern Ireland from their itineraries.
"If ambiguity exists, if explanation is required it will make it much easier for that agent to say, 'I don't need to be bothered with this hassle, it's much easier for me to sell a trip to Cork or Galway or Kerry'," he said.
He added that it had "taken a long time" to build up that tour business in Northern Ireland.
"If you don't make it simple and easily understood there's the potential for that business to be lost."
Joanne Stuart from the Northern Ireland Tourism Alliance (NITA) told MPs there had been no consultation on the issue.
She said there were also concerns about how it would impact cross-border workers like coach drivers.
"A not-insignificant amount of these are non-Irish EU nationals, and under these proposals they too would need a visa for every crossing. How can we justify this?
"Given the skills shortage in this sector we need to make it more attractive, not put those already working here at risk."
www.bbc.co.uk/news/uk-northern-ireland-61162338