MEP Brian Crowley has announced his retirement after more than 25 years in politics.
At a press conference in the Rochestown Park Hotel this afternoon, he announced that he will not be contesting the European elections this May.
The announcement puts an end to speculation about his status after losing the Fianna Fáil party whip in 2014, and being unable to attend parliament since then due to poor health.
Mr Crowley said that he will be returning to work in Brussels and Strasbourg in the coming months, but will not be putting himself forward for selection for Fianna Fáil or running in the election in May.
He said his health will not allow him to give the people of Ireland South the campaign that they deserved and that he wanted to run.
Mr Crowley was first appointed to the Seanad by Taoiseach Albert Reynolds in 1992.
He subsequently topped the poll at his first run in the 1993 European elections. He repeated that feat again at the next four elections.
He served as co-president of the Union for Europe of the Nations grouping until 2009, when Fianna Fáil joined the ALDE group.
The move caused friction with the party leadership at the time and culminated with Mr Crowley leaving the ALDE group and joining the European Conservatives and Reformists group in 2014.
He was then ejected from the Fianna Fáil parliamentary party.
Speaking today Mr Crowley said he didn't inform Micheál Martin about his decision and hasn't spoken to him since 2014.
However, he said that he supports him as party leader and believes he has done a good job under hard circumstances.
Mr Crowley, who was paralysed from the waist down in an accident and has been a wheelchair user since he was 16, was unable to attend parliament since the summer of the last election due to poor health.
He had previously missed part of the previous term but was well enough to return and contest the election in 2014.
Following the announcement today, Fianna Fáil Leader Micheál Martin paid tribute to Mr Crowley's long career of public service.
“Brian’s life has been one of service to his community and to the country. His personal story has also acted as an inspiration to many people as he refused to allow his disability, following an accident at 16 years of age, to hold him back from his vocation of public representation, in any way."
“Brian was dedicated and dogged in serving the people that voted for him in great numbers. He approached all issues with great enthusiasm and detail," Mr Martin said.
“In recent years, Brian’s health has suffered and I understand that his decision to retire will not have been an easy one, but I also know that Brian is a person of great resilience and great faith and I wish him the very best as he works to achieve a full recovery to good health."
Attention will now turn to who will replace him on the Fianna Fáil ticket this May.
Former Cork County Mayor Seamus McGrath confirmed his intention to seek a nomination this afternoon, while Cork North Central TD Billy Kelleher indicated yesterday that he is interested too.
That move is likely to cause friction with Fianna Fáil leader Micheál Martin, who does not want TDs running as he does not want any by-elections.
Wexford county councillor Malcolm Byrne is also expected to contest a selection convention set to be held in the coming weeks.
Sitting MEPs Deirdre Clune and Seán Kelly, Fine Gael, and Liadh Ní Riada, Sinn Féin, are all expected to run again.
The Ireland South constituency is going from four to five MEPs owing to a redistribution of the United Kingdom's seats to remaining EU member states after Brexit.
However, should the UK government seek to extend the negotiaion period, the final MEP elected in Ireland South and Dublin may not be able to take up their seats until the UK formally leaves.