Simon Harris says Sinn Féin had the opportunity to nominate Mary Lou McDonald to be Taoiseach, but didn't as she would not have achieved a Dáil majority.
The comments come after the Cabinet reshuffle, in which the Higher Education Minister was tasked with leading the Department of Justice while Minister Helen McEntee takes maternity leave.
He joined Gavan Reilly On the Record to discuss the government changeover, the opposition's "populist" politics and his new responsibilities as interim Justice Minister.
Minister Harris stressed that, while there has been a change in Taoiseach and a minor Cabinet reshuffle, there has not been a change of government.
"There hasn't been a general election", he explained.
"The mandate that this government and Dáil has remains the same from the 2020 election."
He added: "Really what yesterday was about was seeing the government into the second half of its term, but continuing to deliver an agreed programme between Fine Gael, Fianna Fáil and the Green Party."
Minister Harris said that he doesn't think the leadership changeover was too "pally", "unless they fall for some of the spin or nonsense put out by some of the populist opposition parties".
"The reality of the situation is any member of Dáil Éireann could've been nominated to be Taoiseach yesterday, and had Sinn Féin nominated Mary Lou McDonald, she would've resoundingly lost", he said.
"When you hear parties like Sinn Féin saying, 'we won the last election' - you didn't."
"They could've nominated here."
He said that Ms McDonald doesn't have the command of the majority in Dáil Éireann.
"Had they wished to test that theory yesterday, they could've nominated her", he said.
He said that yesterday's vote showed that the government has a "very strong working majority", buffeted by the support of some Independent TDs.
The decision to add another portfolio to Minister Harris's workload was partially dictated by the restrictions on the number of people that can be in Cabinet.
Minister Harris said he will have support in maintaining both Departments over the next six months .
"The Taoiseach was very clear that I am to give this job my all", he said.
He plans to bring "energy" and "focus" to key issues such as the Defamation Bill, the Sexual Offences Bill and Garda recruitment.
The new Justice Minister also wants to further plans to supply Gardaí with body cameras.
"I can absolutely assure your listeners and assure the people of Ireland that the security and safety of citizens ... will be my absolute main priority", he said.
Listen back to the full conversation here.
Main image shows Minister for Further and Higher Education Simon Harris briefing media in the courtyard of Government Buildings in June 2022. Picture by: Sasko Lazarov / RollingNews.ie