Northern Ireland’s Chief Constable, George Hamilton, has repeatedly said that a hard border would be damaging for the wider peace process.
He has said that any new border infrastructure would be seen as “fair game” for attack by dissident republicans.
In an interview last year, he also put the border in the context of the Good Friday Agreement.
“If you put up significant physical infrastructure at a border, which is the subject of contention politically, you are re-emphasising the context and the causes of the conflict,” he said.
“So, that creates tensions and challenges and questions around people’s identity, which in some ways the Good Friday Agreement helped to deal with.”
The Democratic Unionist Party (DUP) and some Brexit-supporting Conservative MPs say the issue of a hard border need not arise as they believe it can be overcome by a range of administrative and technical measures.
The DUP also says the real threat to the spirit of the Good Friday Agreement is the imposition of the backstop.
Sinn Fein has said any hard border in Ireland will lead to further calls for a referendum on Irish unification and is pushing for a border poll to be held in Northern Ireland if there is a no-deal Brexit.