Socialist TD Joe Higgins has been chosen to sit on the banking inquiry.
The Dublin West TD has been nominated by his colleagues in the Dáil's Technical Group to take up the seat vacated by Stephen Donnelly.
Deputy Donnelly quit the inquiry over the weekend, in protest at the Government's decision to add two extra senators to the committee to guarantee its own majority.
Higgins has been critical of politicians and bankers in the past, and said he will bring that to the inquiry.
"I believe that what I call the dictatorship of the European financial markets has to be a factor here," he said.
"But I am prepared to sit, and quiz, and question in the inquiry, those individuals who were central to political and economic events at the time, and interrogate them very strenuously."