The Taoiseach has said that records show Dara Murphy attended the Dáil and was present at Leinster House for at least 120 days last year.
Leo Varadkar said that the Fine Gael TD's attendance is the amount required under law.
Deputy Murphy has said that he has been compliant with rules for attendance at Leinster House, after opposition parties called for an investigation over his Dáil attendance.
The Taoiseach said that Deputy Murphy will assist in any investigation carried out.
"He's not going to be tried by media but he is willing to cooperate with any statutory investigation and he is to stand over the fact that he was present for at least 120 days last year," he said.
In a statement released on Saturday night, Mr Murphy said he as a TD he is entitled to have another occupation.
“Following recent media and political commentary, I wish to state that at all times I have been compliant with rules for attendance at Leinster House.
I will continue to provide any evidence required to the appropriate authorities. I attended the required 120 days at Leinster House in 2018 and should achieve the requisite number for 2019 and will make the statutory return when due,” he said.
“As a Minister of State, I was precluded under law from any other occupation. As a TD, I (and every other TD) can have another occupation. Many of my colleagues in Dáil Éireann do so - some colleagues have legal, medical, business, farming etc interests,” he added.
“I have remained in the political environment. Fine Gael nominated me in 2015 as a European Peoples Party (EPP) Vice President and I was successfully elected. The EPP is the largest political group in Europe with more than 80 member parties,” Mr Murphy said.
“Most Irish political parties have an affiliation to a European political grouping and various members of the Oireachtas engage with their own groups in different capacities.
"In October 2017, I was elected as EPP European Election Campaign Director. European elections and politics are very important for all the people of Europe and this is particularly the case for Ireland at this time in our history,” he added.