The Taoiseach has said former TD Dara Murphy should return his expenses if any investigation finds he broke Dáil rules.
Leo Varadkar said the clerk of the Dáil could investigate concerns that have been raised around the claiming of Mr Murphy's expenses.
It emerged in recent weeks that Mr Murphy claimed his full expenses despite being largely absent from the Dáil over the past two years.
Neither SIPO or the Dáil's ethics committee can investigate now that Dara Murphy is a former politician, after he officially resigned as a TD earlier this week.
Speaking today, the Taoiseach said claims around his Fine Gael colleague's attendance should be examined.
He explained: "My view is that an investigation should happen first, and if the investigation found that he broke the rules than absolutely he should pay it back.
"My view is always due process and natural justice - you have an investigation and then you have an outcome; you don't have an outcome and then have an investigation and then maybe change the outcome again."
Mr Varadkar added: "I think there are two questions here. One is did Dara Murphy break the rules or not? That requires an investigation... and he's willing to cooperate with that.
"There's a wider question as to whether the rules are too lax - and I think they are too lax."
Since taking up a role as the European People Party's campaign director in September 2017, Dara Murphy continued to draw his full Dáil salary of more than €94,000 a year, as well as more than €50,000 worth of annual allowances.
Figures released by the Houses of the Oireachtas show that he only attended 24 out of 70 sitting days in the Dáil between January and September - the lowest number of any TD.
Mr Murphy has insisted that he complied with Dáil rules at all times regarding his attendance.