Vital cross-border sharing of policing expertise is going to become extremely difficult post-Brexit, former police chief Judith Gillespie has warned.
The former Police Service of Northern Ireland deputy chief constable and member of Ireland's Policing Authority said that Brexit is going to pose many challenges for law enforcement.
In an interview with the Press Association, Ms Gillespie said one of the main threats to policing post-Brexit will be the sharing of important experience between the Garda and the PSNI.
Recent Garda superintendent and chief superintendent promotion competitions have seen a number of PSNI officers being successfully recruited.
Ms Gillespie said this was a welcome step in terms of "sharing policing experience across the two jurisdictions where there are unique and shared challenges."
"But post-Brexit this movement of staff will become even more difficult than it is now," warned Ms Gillespie.
She added: "I think Brexit is going to pose so many challenges for law enforcement - European arrest warrants, exchange of information, intelligence, fingerprints, DNA, all those things. I have much concern.
"And any type of hard border will have very significant costs both north and south.
"In the context of shrinking public sector costs that is going to be a real challenge - to continue to deliver policing, in the context of additional costs to policing a hard border. It is a big concern," she said.
Ms Gillespie, who retired from the PSNI in 2014 after 32 years, joined the Republic of Ireland's Policing Authority in January 2016.
She said the Garda oversight body has a really important part to play "as a critical friend and in ensuring pace in delivery of change".
"That's important not just for the public but also for the very many good people within the organisation," she added.
Since joining the oversight body the Garda has been hit by a number of controversies and Commissioner Noirin O'Sullivan has faced calls to resign.
However, Ms Gillespie believes that the commissioner should be given a "fair chance" to transform the force - but warned that the Policing Authority will be watching her performance "very closely".
"I think the Commissioner should be given a fair chance to prove she can transform and modernise the organisation.
"I think Noirin is an incredibly resilient person. I have known her for many years. I think she has had a very difficult job to take over with the history of the organisation.
"I do think she has had difficulties with her own team as well and that has posed internal challenges as well as external challenges she has had to face.
"I think she has to be given time to turn the organisation around. You are never going to be able to make these cultural changes overnight. It is going to take time," said Ms Gillespie.
However she added: "There will soon be a time when we expect to see tangible evidence of changes delivered, and the Authority is watching very closely in terms of the implementation of the Garda Inspectorate report."