The prime minister of Ireland has said he is stepping down as leader of the Fine Gael party, kicking off a succession contest between two younger ministers.

Enda Kenny - who had already announced he would not lead Fine Gael into the election - said on Wednesday that he would remain prime minister during the contest, due to be concluded on June 2, and subsequent talks with government officials backing the government.

"I would like to stress the huge honour and privilege that it has been for me to lead our party for the past 15 years, in opposition and into government on two successive occasions," Kenny said in a statement.

Kenny, prime minister since 2011 and leader of his party for almost 15 years, is expected to be replaced by either Leo Varadkar, the social protection minister, or Simon Coveney, the housing minister.

Kenny was due to step down at midnight to become acting party leader until a successor is chosen.

Voter backlash

He has overseen Ireland's turnaround from entering a humiliating three-year state bailout, just months before he came to power, to becoming Europe's fastest-growing economy for the past three years.

But at a parliamentary election last year, Fine Gael suffered a backlash from voters who felt the recovery was passing them by.

It lost a quarter of its seats, only returning to power as the senior party in a fragile minority government.

Colleagues are counting on a new leader reviving their fortunes after falling marginally behind rivals Fianna Fail in most surveys.

The race is set to be dominated by the two declared candidates: Varadkar, 38, and Coveney, 44.

Whoever wins will take over as prime minister, subject to a parliamentary vote, at least until the election.

Fianna Fail agreed last year to abstain in key votes to let the minority government run until late 2018.