The former chairman of the Labour Party has joined Fianna Fail claiming the party has learnt lessons from the past.
Colm Keaveney, a TD for Galway East, first rebelled over Budget 2013 and then quit his former party claiming its time in government has turned into a political charade.
"It has become increasingly clear to me that the only organisation in Irish politics that seems genuinely interested in learning from the lessons of the past and putting fairness at the heart of policy making is Fianna Fail," he said.
Mr Keaveney said he would support Fianna Fail's renewal following a hammering in the 2011 general elections and highlight what he said are deeply unfair decisions being made by the Labour-Fine Gael Government.
The switch was confirmed following a meeting of the Fianna Fail parliamentary party in Leinster House this afternoon.
Fianna Fail leader Micheal Martin said he was struck by Mr Keaveney's commitment to fairness and his determination to make his time in politics count.
"He is someone who is deeply motivated by the impact politics can have on individuals and communities and wants to be part of an organisation that is committed to a fairer way to recovery," Mr Martin said.
On Twitter, ahead of his unveiling by Fianna Fail, Mr Keaveney posted a message in Latin
"Forsitan et nostrum nomen miscebitur istis - Audentis Fortuna iuvat! (h/t Ovid & Virgil)", he said, which in part translates as "fortune favours the brave".
Mr Keaveney caused the Labour hierarchy headaches for several months after refusing to support the budget but remaining on as the chairman until the summer.
In his resignation from the party he accused the coalition of targeting cuts at those least able to defend themselves and he also said he was opposed to some of the reforms in the new abortion legislation.
He said he was becoming more alienated the more he tried to promote Labour values.
Labour has lost a string of representatives since it took its biggest electoral success in early 2011.
Former junior health minister Roisin Shortall quit after clashing with Health Minister James Reilly over the designation of primary care centres in his constituency.
Patrick Nulty was kicked out of the parliamentary party after voting against the coalition's first budget in December 2011.
Nessa Childers MEP quit in April, claiming the party was hurting people.