Brexit could lead to "some civil unrest" in Northern Ireland, particularly in relation to the border, former PSNI Assistant Chief Constable Peter Sheridan has warned.
Mr Sheridan, who is now the head of Cooperation Ireland, said protests can become more dangerous if people feel their identity is being compromised.
Mr Sheridan was addressing TDs and Senators in the Republic at the Joint Committee on the Implementation of the Good Friday Agreement.
“I don’t want to overstate it, but there is a danger that ultimately this could lead to some civil unrest, particularly in relation to the border,” Mr Sheridan said.
He said the process in Northern Ireland was still fragile and said there was the need to minimise barriers to trade and ensure the free movement of people. He added that issues of identity could also occur.
“It is still a fragile peace protest,” Mr Sheridan said.
“There are already protests along the border. The history of this place is that protest can become much more dangerous as this goes on. That’s why I raised the issue of identity. If people feel that their identity is being threatened or compromised, we need to be careful of those things, and not be complacent about them.
“That’s not to overstate that there’s going to be some sort of conflict arising, but we have to be aware that it’s not that long that we were in conflict around a lot of these issues.”
However he said the violence of the past was "not going to break out again".
Mr Sheridan retired from the PSNI in 2008 having spent 32 years policing in Northern Ireland.
Before retiring he was responsible for the Crime Operations Department, which included serious and organised crime investigation including terrorist investigations.
He has been chief executive of the Cooperation Ireland charity since 2008.