Irish Green Party leader Ermon Ryan will resign, Irish broadcaster RTÉ reported.
The announcement would mean Mr Ryan becomes the second leader of the Republic’s coalition government to step down this year.
Former Prime Minister (Prime Minister) Leo Varadkar resigns as Fine Gael leader in April.
Mr Ryan’s decision follows local and European elections in which the Greens lost two MEP seats.
The party’s number of local councilors has also been halved.
Mr Ryan has been leader of the Irish Green Party since 2011 and was first elected to the Irish Parliament in 2002.
He has been the TD for Dublin Bay South since 2016.
“A new generation of leaders”
Speaking outside Leinster House on Tuesday, Ryan said he would resign to “pass the torch to a new generation of leaders”.
While he will remain as environment and climate minister, he said the Greens’ “focus in the coming months should remain on delivering affordable housing, health reform and climate action”.
Mr Ryan said he was “proud of what we have achieved” and that he was “a champion for climate justice in developing countries on the world stage”.
He added that he “cannot continue to work the long hours of a public representative” and that he also wanted to fulfill his “childcare obligations at home”.
‘Relentless attack’
Mr Ryan went on to say his party had been “under relentless attack, particularly on social media”.
“After any of our posts, there seems to be an effort at times to coordinate attacks in the comments section.
“I decided to ignore most of them, even though they contained vicious remarks about my recently deceased father.
“I think it poisons the public’s thinking about our agenda, not just our party’s thinking,” he said.
He added that he was optimistic about the future, although he emphasized that “if you just live in an algorithm-driven, polarized online world, people may despair about the future of our democracy.”
“A decent politician”
Speaking at Leaders’ Questions in the Dáil this afternoon, Taoiseach Simon Harris said Mr Ryan had “had a positive impact on Irish politics”.
“He has played an important leadership role in this alliance and I want to acknowledge that,” Mr Harris said.
The Prime Minister described Mr Ryan as an “honest, sincere, dedicated and decent politician”.
“He is a man of substance, a man who has had a positive impact on Irish politics and I completely respect and understand his reasons and I just wish him the best,” he added.