Simon Harris is set to become Ireland's next prime minister after the governing Fine Gael party appointed him as its leader on Sunday, following an uncontested election. 

The 37-year-old said it was the "absolute honour of my life" to be appointed party leader, and his rise to the country's top job is expected to be confirmed when the Irish parliament returns from recess early next month.

He will take over from Leo Varadkar, who announced his resignation on Wednesday in a move pundits described as a "political earthquake" in the EU member. 

"After seven years in office, I am no longer the best person for that job," said Varadkar, 45.

"My reasons for stepping down now are personal and political, but mainly political," he added, without elaborating.

Within hours, Harris had secured endorsements for a leadership bid from a majority of Fine Gael party colleagues, prompting his potential rivals to rule themselves out.

With nominations closing at 1300 GMT Sunday and no challengers emerging, party official Willie Geraght declared Harris as winner hours later at a convention in Athlone, west of Dublin.

Deputy party leader Simon Coveney said the new leader, and prime-minister-in-waiting, was a "really charismatic" politician who was "ideally placed" to revive his ailing party's fortunes.

Upon his coronation, Harris told the centre-right party's members that he would repay their faith with "hard work, with blood, sweat and tears, day in and day out with responsibility, with humility and with civility."

Setting out his priorities, Harris insisted that Fine Gael "stands for law and order" and told members he wanted to "take our flag back" from nationalists, to loud cheers.

He also said that he would pursue a "more planned and sustainable" immigration policy, following increased tension over the issue, and that he would "fight against the dangers of populism".

On the international front, he called for an immediate ceasefire in Gaza and condemned Russia's "horrific illegal invasion of Ukraine".

Formidable to-do list

With Fine Gael and its government coalition partners — center-right Fianna Fail and the Green Party — forming a majority in the Dail (the Irish parliament), Harris will be formally elected as premier on April 9 when the Dail returns.

Harris will become Ireland's youngest ever "taoiseach" (pronounced "tee-shock" — a Gaelic word for "chieftain" or "leader") beating Varadkar who was 38 when he took the role in 2017.

Harris' dramatic procession to the job of taoiseach crowns a meteoric political career.

Born in 1986, he grew up in a small town near Dublin where he got a first taste for politics when campaigning for disability services for his autistic brother.

He entered the youth branch of Fine Gael at the age of 16, was elected to parliament as a 24-year-old in 2011 and appointed health minister in 2016 aged just 29.

"In many ways, my career has been a bit odd... life came at me a lot faster than I expected it to," he told Hot Press magazine in a 2022 interview.

"He has huge energy and huge ambition," a Fine Gael party colleague told the Irish Times newspaper this week. 

The new taoiseach will face a formidable to-do list, including tackling housing and homelessness crises amid intensifying criticism of government policy on asylum seekers. 

With a reputation for slick communication and social media skills, Harris will also urgently seek to galvanise his struggling party which lags third in polls as key elections loom.

Ireland votes in both local and European parliament ballots on June 7, while the next general election must be held by March 2025.

Fine Gael slumped to third place at the last general election in 2020, well behind the largest party, the leftist-nationalist Sinn Fein — former political wing of the paramilitary IRA — who still lead in polls.