Chief Constable of the PSNI George Hamilton has said some politicians in Westminster do not understand the potential danger posed by terrorism in a post-Brexit Northern Ireland.
In an interview with the Sunday Times, Mr Hamilton outlined his frustrations with a feeling towards the Troubles and Northern Ireland that it "is sorted and we don't need to worry about it".
"Actually we're working flat out 24/7 to keep a lid on it," he said.
Mr Hamilton said any post-Brexit border infrastructure could become a target for dissident republicans.
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Asked if the thought the Government's understood the potential impact of a future border, Mr Hamilton said: "I'm not sure all of them do. I have a concern some may see issues to do with the Irish border as literally peripheral, not just geographically but in terms of impact."
One issue he called on to be addressed was a need for more investment and resources for the PSNI, at a time when Revenue and Customs and the UK Border Force have been given thousands of extra officers.
The PSNI is requesting over 400 extra officers, extra vehicles and equipment, and the sale of three unused police stations in the border regions to be suspended.
The chief constable's comments echo remarks he made in June before the Northern Ireland Affairs Committee in which he warned of the threat from organised crime and terrorism, in which he said the PSNI was "in the dark" about future border arrangements.