East Londonderry MP Gregory Campbell has called on the Tanaiste to explain why officials from his department visited a republican prisoner in Maghaberry on two occasions.
Simon Coveney, who is also Minister for Foreign Affairs and Trade, raised the two-year detention of Tony Taylor on the floor of the Dail after a recent visit he made to Taylor's home city of Derry.
Taylor, who has two terror-related convictions, has been in prison since March 2016 after his licence was revoked.
Mr Coveney said he intended to write to the Secretary of State Karen Bradley voicing his concerns about Taylor's ongoing detention "without being charged with or convicted of any new offence".
Mr Coveney added: "I am also aware that there is a level of concern in the nationalist and republican community in Northern Ireland about the basis for and nature of Mr Taylor's ongoing detention.
"They have all been reflected in our ongoing engagement with the NIO on the matter."
DUP MP Mr Campbell said Mr Coveney's department "should not be getting involved in this matter".
"It wasn't his place to do that, it's not in his brief," he said.
"Simon Coveney seems to have ignored the fact that this man has twice been convicted of serious terrorist-related offences and after the second time when he was considered for parole, the parole board said he still presented a danger to the public.
"Despite those factors, these visits went ahead.
"They will be taken by many people in Northern Ireland as some form of succour or support, or at least ambivalence towards Tony Taylor and his previous actions, no matter what way he tries to explain that's not what it was."
"What Simon Coveney has to answer is why his officials were visiting someone who has been twice convicted of terrorist offences and is still considered a risk to the public."