Former Labour Party TD Colm Keaveney will join Fianna Fáil today, Independent.ie can confirm.
Mr Keaveney has been in talks with Fianna Fail party leader Michel Martin since the Summer.
The Galway East TD is expected to be announced as a party TD today after his name is put to a special parliamentary party meeting.
He will be given a position on the party frontbench in the area of health, education and disabilities.
The signing is a significant boost to Mr Martin and comes after a series of meetings with party officials.
Mr Keaveney will be the Fianna Fáil candidate in the next general election in the newly conference Galway East-Roscommon South constituency.
The former Labour TD will bring the number of Fianna Fáil TDs up to 20.
Mr Keaveney was elected as a Labour Party TD in 2011 and subsequently became the party chairman.
He enjoyed a fraught relationship with the Labour leadership as he was frequently critical of the party's policies in Government.
He resigned the party whip in the wake of last year's budget to become an Independent TD and eventually resigned from the party and as chairman.
The deal to get Mr Keaveney to join Fianna Fáil has taken almost six months to come off.
The Galway East TD has also been meeting with senior party officials since the summer.
He had two meetings in July and August with Mr Martin.
His personal assistant, Colm Hynes, was also involved in meetings with Fianna Fáil general secretary Sean Dorgan.
"Fianna Fail come sniffing around to Colm during the summer wanting a meeting. But Colm has been kicking lumps out of Fianna Fáil for years," a local party source said.
Mr Keaveney was considering a run in the European elections in new Ireland Midlands-North-West constituency, but was thought to have backed off the idea due to the logistics and expense involved.
Fianna Fáil TD Michael Kitt has said he has not ruled out running again despite the imminent arrival of Keaveney.
"It's early days yet," he said.
Mr Kitt said he had no difficulty with the imminent arrival of Mr Keaveney.
"We're a broadly based party. A new member broadens the support," he said.
Labour Leader Eamon Gilmore today declined to comment on the news.
However a senior party source said the decision has come as a "surprise" to Mr Gilmore.
"He would have expected Colm Keaveney to run as an independent, I think the last thing he thought would happen is that he would join Fianna Fáil."