The Communications Minister Richard Bruton has said his party colleague Dara Murphy has serious questions to answer.
It comes after he claimed full expenses despite being largely absent from the Dáil over the past two years.
The Oireachtas Committee on Members Interests has been asked to investigate Deputy Murphy's attendance record.
Minister Bruton said Deputy Murphy needs to show his expense claims were justifiable.
Mr Bruton said: "Now he needs to account for what claims he made and whether those claims were justifiable.
"I mean a lot of questions have surfaced in the media and they do have to be answered, I think it's important that the Committee on Members Interests investigate this and thrash it out. I mean people ultimately have to be accountable for what they do."
Fianna Fáil has said there is no evidence to show that the Fine Gael TD did his job to the best of his ability.
Deputy Murphy claims he has been compliant with Dáil attendance rules.
Fianna Fáil Chief Whip Michael Moynihan has written to the Oireachtas Committee on Member's Interests asking it to investigate Deputy Murphy's attendance record.
Deputy Moynihan said: "He hasn't been operating as a full-time TD for the people of Cork North Central and he was elected to do that job in 2016.
"We don't see any signs to say that he was performing his duties as a TD in terms of Dáil debates and Dáil questions."