Transport Minister Shane Ross has warned that a hard border on the back of a disorderly Brexit could provoke bomb attacks.
The comments came as Tánaiste Simon Coveney described British prime minister Boris Johnson's push to scrap the backstop as a “totally unreasonable position” as the two Governments' positions over Brexit continued to harden.
Irish and British ministers disagree over whether reasonable proposals have been put forward to replace the backstop - the guarantee to keep the North aligned to the EU and prevent a border.
The worsening relations come ahead of a showdown in the House of Commons next week over Mr Johnson's attempt to shut down parliament as he drives through his Brexit agenda.
Taoiseach Leo Varadkar and Mr Johnson are also still set to have their first face-to-face meeting next month.
As he continued a tour of EU capitals to hammer home Ireland's concerns about Brexit and the importance of the backstop, Mr Coveney hit out at the British Government led by Boris Johnson.
Arriving at a meeting of foreign ministers in Helsinki, Finland, he said: “We all want to get a deal but, at the moment, nothing credible has come from the UK government in terms of alternatives to the backstop.
“If there are alternatives to the backstop that do the same job, well then let’s hear them. And if we can work out a deal on that basis, so be it. But it’s got to be credible.
‘There’s no country that wants a deal more than Ireland. We want good relations with the UK in the future. We share a lot of responsibility in the island of Ireland, north and south, that Brexit is very disruptive towards.
It cannot simply be this notion that we must have the backstop removed and we'll solve this problem in the future negotiations, without any credible way of doing that. That's not going to fly.
Earlier, he told Newstalk: “Boris Johnson is outlining a very clear and firm position but it is a totally unreasonable position that the EU cannot facilitate and he must know that.”
Mr Coveney said of Mr Johnson's suggestion to have two days a week of negotiations on Brexit: “I’m sure if he wanted five days of negotiations a week, the EU would be okay with that.
"Michel Barnier is there as the chief negotiator for that purpose, he has a team that’s ready to go."
Mr Coveney also held a 45-minute meeting with his British counterpart in the Finnish capital, reiterating that the backstop was not for renegotiation.
Britain has said technological options to border inspections could be possible by the time the backstop is needed. However, Dublin denies credible alternatives have been put forward.
But British Transport Secretary Grant Shapps insisted Britain had made proposals to replace the backstop, and it was wrong for Ireland to claim otherwise.
"It's just not true," he said.
So it's a cover when they keep saying: 'You are not putting forward ideas'- we are putting forward ideas.
Elsewhere, Shane Ross has warned that a hard border could result in bomb attacks.
Speaking to the Journal about a recent explosion in Co Fermanagh, which was deemed a failed attack on police officers, the Independent Alliance minister said: “That’s what maybe a hard border would provoke, something like that.”