Tánaiste Simon Coveney has labelled UK Conservative MP Jacob Rees-Mogg as "ill-informed" for suggesting people crossing the Northern Ireland border could be "inspected" after Brexit in the same way as "we had during the Troubles".
The Minister for Foreign Affairs said that Mr Rees-Mogg, a Tory backbencher and senior Brexiteer, was "ill-informed" after the comments surfaced in a video posted on Twitter.
In the clip, Mr Rees-Mogg is shown at a town hall-style discussion on Brexit, talking about the border, which has proved one of the most difficult parts of the Brexit negotiations with Brussels to solve.
Both sides have ruled out a hard border - which would contravene the Good Friday Agreement that ended decades of fighting in Northern Ireland.
In the clip, Mr Rees-Mogg says that the UK could continue with "historic arrangements" to avoid a loophole that would allow people to get into the UK.
He continues: "There would be our ability, as we had during the Troubles, to have people inspected.
"It's not a border that everyone has to go through every day. But of course for security reasons during the Troubles, we kept a very close eye on the border to try and stop gun-running and things like that."
Mr Coveney highlighted the clip on Twitter, saying: "We have left 'the Troubles' behind us, through the sincere efforts of many, + we intend on keeping it that way."
Fears of a return to violence have been raised if the Good Friday Agreement is damaged by the imposition of a hard border on the island of Ireland after Brexit.
It’s hard to believe that a senior politician is so ill informed about Ireland + the politics of the #Brexit Irish border issue that he could make comments like these. We have left "the troubles" behind us, through the sincere efforts of many, + we intend on keeping it that way. https://t.co/yuZYDFiWOq— Simon Coveney (@simoncoveney) August 25, 2018
The EU's suggested solution to the problem - a common regulatory area for goods and customs with the rest of the EU - has so far been rejected by the UK as "annexing" Northern Ireland.
British Prime Minister Theresa May has been adamant that such a move creating a border down the Irish Sea would be unacceptable to the British government.
In return, Mrs May's suggested solution, a complex customs arrangement that would see the UK collect duties for the EU, has been dismissed by Brussels.