Éamon Ó Cuív has been appointed deputy leader of Fianna Fáil.
The Galway West TD and former government minister is a grandson of party founder Eamon de Valera. He replaces Mary Hanafin, who failed to retain her seat in the general election.
Mr Ó Cuív was among three new frontbench appointments announced by Fianna Fáil leader Micheál Martin.
Michael McGrath, Mr Martin‘s running mate in the Cork South Central constituency, will take over as the party‘s finance spokesman.
Sean Fleming, TD for Laois-Offaly, has been appointed public expenditure and public sector reform spokesman.
Mr Martin said the changes reflected the work done by the three since the death of the former finance minister Brian Lenihan.
“I am confident that all three will provide robust and constructive challenge to the government in the next term of the Dáil, in addition to strong leadership within the Fianna Fáil party as we work to renew the organisation across the country,” he said.
“Our country faces enormous challenges on the budgetary, banking and economic front,” Mr McGrath said. “I am determined that Fianna Fáil will play a positive and responsible role on these issues, while at the same time rigorously holding the Government to account for its actions.”