NEW Chief Constable Simon Byrne has warned of the dangers a hard Brexit poses to the stability of Northern Ireland.
Mr Byrne has said he wants answers from London about what he called the "detrimental" impact of a hard Brexit.
"I think we are worried that in the short term a hard Brexit will create a vacuum which becomes a rallying and recruiting ground for dissident republicans and clearly any rise in their popularity or their capability would be very serious"", Mr Byrne said.
Adding that "on 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."
Mr Byrne, who took over from George Hamilton at the start of July, said that the PSNI were having discussions with senior civil servants to make plans for all eventualities.
"If we go to a 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.
"There are a small number of people here, particularly dissident republicans, that are intent on a particular ideology and do present operational challenges and a risk to safety right across Northern Ireland," Mr Byrne added.
DUP MP Jeffrey Donaldson last week urged the taoiseach Leo Varadkar to talk directly to Westminster for an all-island solution to the threat of a hard border.
The party's chief whip said the Irish government should be exploring a joint arrangement for agrifoods "other than an indefinite backstop".
Meanwhile, chancellor Philip Hammond has warned that a "do-or-die" departure from the EU on October 31 would spell "chaos" at the ports.
Speaking to the BBCs Panorama team, in an interview due to be aired on Thursday, Mr Hammond claimed Boris Johnson has no way of controlling events in a no-deal scenario.
It is believed that the Treasury is concerned that Mr Johnson, who remains the front runner in the Tory leadership race, has not considered the implications of his plans to leave the EU at the end of October with or without a deal.
The Treasury have warned that is he does go ahead with his plans that the International Monetary Fund will file a negative assessment of Britain's economic prospects that will lead to an immediate downgrade of the UK credit rating.
