A criminal "safe haven" could be created at the Border in the event of a no-deal Brexit, a senior PSNI office has warned.
PSNI assistant chief constable Tim Mairs also expressed concern about losing the use of European arrest warrants should the UK crash out of the European Union.
Addressing a Brexit seminar of the Northern Ireland Policing Board in Belfast on Thursday, Mr Mairs warned that the loss of the warrant system or the ability to share information risked creating "a perception of a safe haven" on the Border where "criminals can commit a crime in one jurisdiction and get to the other where they feel they are beyond prosecution".
Mr Mairs said this week the PSNI was seeking to bring five people back to face charges for a range of serious offences using European arrest warrants.
“That demonstrates how critical that power is because it sends a message to criminals that there is no hiding place,” he said. “While you can commit an offence and try to flee the jurisdiction, we are able to reach into other jurisdictions and we are able to bring people back.”
He also recalled that before the use of the warrants it was difficult to achieve extradition on the island of Ireland, with some cases taking years. However, he said extradition cases could now be resolved “in a matter of weeks or months”.
Mr Mairs said that within the current withdrawal agreement, "there is a commitment to a future security agreement in the United Kingdom and Europe and a commitment by and large to attempt to create as similar an arrangement as possible". But even in this situation, he said, there was a "likelihood" these arrangement would not be as effective as they were.
“This becomes a lot more acute for us in a no-deal scenario, where many of those powers would cease quite suddenly.”
Mr Mairs said it was clear from the assessment of UK police commanders that in the event of a no-deal, “whatever we put in place will be suboptimal to what we currently have”.
“In some cases we will lose capabilities and in other cases things we could have done previously, such as the checking of criminal records, which could be done in a matter of days, would take months and months,” he said.
“We would see a lot more bureaucracy, and things would slow down and become more complicated.”
Mr Mairs did not specifically mention dissident republicans but said, “We believe that infrastructure and checks at or near the Border would likely generate resistance and the potential for a violent response and attack”.
He said currently there were some North-South differentials that were exploited by organised criminals and “we believe where the differentials increase it is likely that that exploitation will similarly increase”.
Mr Mairs stressed the “critical” importance of maintaining and enhancing the relationship between the PSNI and Garda.
“If we can maintain our ability to work collaboratively on the island of Ireland and actually wider across Europe and Great Britain, then we believe we can effectively respond to crime as it emerges.”
Mr Mairs said Garda commissioner Drew Harris and the PSNI chief constable George Hamilton were "very vocal on continuing the strong relationships" between the two forces and were "absolutely committed to continuing to work together through this period of uncertainty".