A post-Brexit hard border would be a "disaster" for Ireland, former Minister for Foreign Affairs Dermot Ahern has warned.
Mr Ahern told RTE's The Week In Politics he believes "one way or another" there is going to be some sort of hard border between the North and South.
He said such a border "would be terrible for us".
"There will be a hard border of some sort and there will have to be checks, particularly on the southern side. That would be a disaster for us," the retired Louth TD said.
Mr Ahern added: "Whoever decided to put that referendum before the people in Britain didn't think out the implications for Ireland, both North and South.
"I think our Government are in a difficult position given that this has been foisted upon them against their will.
"Obviously they have to try and ameliorate the situation for our people. One way or the other, I think it is particularly bad news for border areas."
Meanwhile Garda Commissioner Nóirín O'Sullivan has moved to reassure the public that the Gardaí will maintain their close working relationship with the PSNI and with UK security services to tackle cross border crime, post Brexit.
"Obviously we have a very unique and very close working relationship with the PSNI and the UK security services. Those relationships will continue," Ms O'Sullivan said during an organised crime briefing recently.
She added: "I have met the Chief Constable of the PSNI and my counterparts in the UK in terms of making sure there will not be an impact. We are determined that nothing will really impact.
"We have to be mindful of whatever happens within the EU administration, the impact that it is going to have on European arrest warrants and operating systems for example. By way of reassurance to the public we will continue our relationship with the PSNI."
The Northern Ireland Police Federation, the body that represents rank and file officers, recently warned that a Brexit hard border would place police officers "in the terrorist firing line".
Head of the Federation Mark Lindsay said physical border posts would make officers easy targets for terrorists and harm relations between the police and communities.
British Prime Minister Theresa May has insisted that both the British and Irish governments want to see a "seamless, frictionless border".