The American senator who brokered the peace deal which ended the Troubles has said border controls between Northern Ireland and the Republic would be a backwards step.
Senator George Mitchell said the ability to cross the frontier between north and south was important.
British Prime Minister Theresa May has promised no return to the borders of the past following Brexit but there are concerns of the implications of a hard exit for the movement of people and goods within Ireland.
Following a Brexit, the UK's only land border with an EU state would be in Northern Ireland.
"I believe that the restoration of a militarised border with strict controls limiting traffic back and forth would have an adverse effect on relations within the island of Ireland," Mr Mitchell said.
"The ability to move back and forward across the border that has existed for the past several years has been very helpful in increasing commerce and also in reducing stereotypes on both sides. I think that that would be a step backward for that to occur."
Mr Mitchell , who was President Bill Clinton's special envoy to Northern Ireland, said he did not want to prejudge any deal that may be done on the border, but hoped "constructive and thoughtful leaders on all sides" could reach an agreement that would "permit open access".
Irish Independent
Play
Play
Play
Play
Play