The UK will put an immigration border around Great Britain following Brexit, cutting off Northern Ireland, the leader of the Ulster Unionists has predicted.
ike Nesbitt, whose party opposed Brexit, said this would particularly disadvantage those from Northern Ireland travelling to other parts of the UK.
He also said he believed an electronic customs border between north and south "won't cut it" as smugglers will be looking at ways to beat it.
It came as politicians in the Assembly voted against a motion calling for Northern Ireland to be granted special status within the EU during the Brexit talks. The motion by the SDLP was beaten by just one vote.
Mr Nesbitt was addressing a hearing in Belfast of a House of Lords inquiry into the impact of Brexit on British-Irish relations.
"In terms of the free movement of people, I think the border will inevitably be at the ports and the airports of Great Britain, from Cairnryan, down to Heathrow, which will disadvantage everybody travelling either way, but particularly the citizens of Northern Ireland making their way to the rest of the United Kingdom," the UUP leader said.
"In terms of the movement of goods, electronic won't cut it, because you can be sure as we speak, there are people on both sides of the border gaming how they're going to make a few bob, or a few euro, out of whatever regime that emerges."
At the same hearing, former Justice Minister David Ford signalled that Brexit may make it tougher for the UK to extradite criminals from the Republic, and vice versa, as there is no alternative to the European Arrest Warrant. Yesterday, Martin McGuinness said Europe is adopting a "hardline" approach towards the government over Brexit. The Sinn Fein leader spent last week in Brussels meeting key negotiators from the European Parliament. Exit talks are due to begin next year.
The Deputy First Minister is pushing for special status for Northern Ireland, after 56% voted Remain in the June referendum. He said: "I have to say it was a very hardline position towards the British Government from almost everybody that I met.
"That does not mean to say it will be a hardline position when it comes to triggering Article 50 of the Lisbon Treaty."
During yesterday's debate at Parliament Buildings, DUP member Christopher Stalford, a strong Brexit advocate, ridiculed the idea that certain parts of the UK could gain special status within the EU.
He noted that while Northern Ireland voted Remain, certain constituency areas voted to leave.
"Maybe Co Antrim should stay part of the United Kingdom but the rest should stay part of the European Union," he said.
"This is the logic of saying we should divide the country up into certain areas. Maybe we should carve off the eastern quarter of Belfast and it should stay out of the European Union, but the other three quarters should stay in - this is the logic that seeks to divide. Where does it end - does London secede from the Union too?"
SDLP leader Colum Eastwood told MLAs: "We should be kicking the door in of the British Prime Minister to ensure the interests of the people of Northern Ireland are protected."
The Foyle MLA, who tabled the debate on the need for special status, added: "My strong belief is the only practical place and the best place to control the border into Britain is at Stansted airport, Heathrow airport, any port that you want to name - because it won't be possible to do it here."