The Chief Constable of the PSNI has warned that a hard Brexit will have an absolutely detrimental impact on the peace process.
Simon Byrne said he was concerned about how Brexit will play out in the weeks ahead and was worried a hard Brexit would create a vacuum and a rally call for recruiting dissident republicans.
He warned that a rise in their popularity or capability would be very serious.
"But to get to specifics if we have a hard border the question I have for London, frankly, is how do we police that hard border?
"You'll know how many crossings there are between the two countries, nearly 300 - and that's the official ones. So I think it raises a whole raft of issues around the potential for smuggling." He said.
"If we go into the worst case scenario, apart from the policing dimension, my personal concern is for example understanding the effects on agriculture here, which is so important. If tariffs change and drop we will see the prospect of animals being culled and people going out of business, that may lead to unrest and we are having to protect other agencies as we go to support new arrangements.
"The minute we go into the border in that regard our worry is my officers and staff become a target for dissident republicans."
During a press conference at PSNI Headquarters in Belfast, the Chief Constable was asked if a hard Brexit would have a detrimental impact on the peace process.
"Absolutely detrimental," he replied.
Meanwhile, Mr Byrne has accused loyalist paramilitaries of using women and children as human shields to frustrate efforts to demolish a contentious bonfire.
He condemned what he branded a "cynical ploy" by the east Belfast Ulster Volunteer Force, acknowledging it was a factor in the PSNI's ultimate decision not to move against the bonfire builders.
Mr Byrne was referring to ad hoc events staged during the four-day stand-off with the authorities over a bonfire built in the car park of Avoniel Leisure Centre.
They included a party that saw bouncy castles inflated at the car park entrance and a rally where local women formed a human chain around the bonfire.
The wrangle over the fate of the bonfire ended on Thursday after councillors backed down over plans to demolish it.
Belfast City Council abandoned an attempt to remove the structure when hired private contractors pulled out of the job after menacing graffiti threats were daubed on walls close to the site purporting to identify them.
Loyalists manned the site 24 hours a day during the impasse, barricading the gates a number of times in anticipation of the police moving in.
At a press briefing, Mr Byrne rejected any suggestion the names of the contractors were leaked from within the police, insisting there were "no facts" to support such a contention.
Additional reporting: Press Association