Tipperary TD Jackie Cahill is to stand down ahead of the general election.
It is understood the Fianna Fáil TD told a group of supporters on Sunday night that he would be stepping away from national politics.
In a statement, Mr Cahill said: "After much consideration, I have decided on personal grounds following health advice not to put my name forward in the upcoming General Election.
"I sincerely regret the short notice of my decision, but personal circumstances dictated this. I would like to sincerely thank you for the help and support you have given to me over the years."
Mr Cahill said that it had been "the honour of my lifetime" to serve the people of Tipperary.
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He added: "I am a lifelong supporter of Fianna Fáil, and I am immensely proud of our Party’s historic role in shaping our country. It has been a privilege to be a Fianna Fáil TD and to work every day on behalf of the people that I have been elected to represent.
Mr Cahill said that he didn't believe he had the commitment to the electorate for another five years.
He noted that he was "deeply grateful to my family and friends" and "every member of Fianna Fáil who nominated me to run for the Party to represent us in Dáil Éireann for a third consecutive time.
"I am deeply grateful to all the Fianna Fáil members, supporters, and voters who have backed me over the years."
The selection convention for the Tipperary North constituency, which Mr Cahill had been expected to run in, had been delayed a number of times. It is only one of two constituencies which Fianna Fáil has yet to select candidates.
Mr Cahill, 61, was first elected to the Dáil in the 2016 election and is the chair of the Oireachtas Agriculture Committee.
One party member said: "It's a big blow for the party. Jackie would have had a safe seat there, we may now not keep that seat."