Leo Varadkar has announced he is standing down as Ireland’s prime minister and also giving up his role as leader of the Fine Gael party in the ruling coalition, in a surprise move described by pundits as a “political earthquake” for the country.

Citing “personal and political” reasons, Varadkar, 45, announced his decision at a press conference in Dublin on Wednesday, saying in an at-times emotional speech that he no longer felt he was the “best person” to lead Ireland.

Earlier this month his government suffered damaging defeats in two referendums on references to family and women in the constitution.

Varadkar, who said he was resigning as party leader with immediate effect, is expected to be replaced as taoiseach as soon as his successor as party leader is able to take office.

While his departure will not automatically trigger a snap election, it comes only 10 weeks before European parliamentary and local elections and less than a year before Ireland’s next general election.

Varadkar said: “One part of leadership is knowing when the time has come to pass on the baton, and then having the courage to do it. That time is now.”

In a statement read on the steps of government buildings in the Irish capital, he said: “I believe this government can be re-elected … I believe a new taoiseach will be better placed than me to achieve that – to renew and strengthen the top team, to refocus our message and policies and to drive implementation.”

He added that he had asked for a new leader of the party to be chosen on 6 April, allowing a new prime minister and cabinet to be elected after parliament’s Easter break.

While he was “deeply grateful” for his time in office and “would wholeheartedly recommend a career in politics”, Varadkar said he had reached the end of the road as taoiseach. “Politicians are human beings and we have our limitations,” he said. “We give it everything until we can’t anymore. And then we have to move on.”

Contenders to succeed him as Fine Gael leader and new prime minister include the higher education minister, Simon Harris, who is the bookmakers’ clear favourite; the enterprise minister and former deputy PM, Simon Coveney; the public expenditure minister, Paschal Donohoe, and the justice minister, Helen McEntee.

Varadkar said his reasons for stepping down were “mainly political” but did not elaborate on what they were. Earlier this month, he was widely blamed for a crushing twin defeat at the ballot box, including the biggest ever referendum loss by an Irish government.

The ruling coalition had proposed rewording the 1937 constitution to change outdated references to family and women. Critics said Varadkar had rushed the debate in a “gimmicky” effort to hold double referendums on International Women’s Day, and accused him of presiding over “incoherent messaging”.

Voters rejected the family referendum, with 67% voting no, and buried the other proposal, which related to women’s care-giving role, in an even bigger landslide of 74%. Varadkar later accepted some responsibility, saying: “There are a lot of people who got this wrong and I am certainly one of them.”

Until Wednesday’s resignation, however, the political fallout from the debacle had widely been expected to be limited. Varadkar has also faced increasing discontent within Fine Gael, with 10 of its members of the Dáil Éireann – almost a third of the party’s total – announcing they will not stand again at the next election, which must be called by early 2025.

Fine Gael has lost five recent byelections, prompting some to see Varadkar as an electoral liability. “His legacy will be that of an electoral loser,” Eoin O’Malley, a political scientist at Dublin City University, told Agence France-Presse. “He promised to be a good communicator, but it turned out he was bad at it. He had no clear agenda, and delivered little.”

The main opposition party and former political wing of the IRA, Sinn Féin, has held a wide polling lead over Fine Gael and Fianna Fáil for the last two years, but polls still suggest the coalition stands a fair chance of re-election.

Defenders of Varadkar say critics like O’Malley are unfair. They point to the widespread praise he earned during his first 2017-2020 mandate for rallying EU support behind the backstop mechanism to avoid a hard border with Northern Ireland during Brexit negotiations with the UK.

Liberals also applaud Varadkar for his leading role in a 2018 referendum that legalised abortion – a milestone in Ireland’s transformation from a socially conservative Catholic society to secularism and pluralism.

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His government has overseen a sharp economic recovery from the pandemic but struggled to tackle a decade-long housing crisis and, more recently, the pressure on services from record numbers of asylum seekers and Ukrainian refugees.

On Wednesday, Varadkar said his tenure as taoiseach had been the “most fulfilling time of my life”, adding that his leadership had “made Ireland a more equal and prosperous country”.

Micheál Martin, the deputy prime minister and Fianna Fáil leader, said Varadkar had informed him of his decision on Tuesday. He described it as “unexpected” but said he fully expected the government to run its full term.

Opposition leaders in parliament called for an immediate election, saying the government had run its course. But Varadkar insisted the office of taoiseach was elected by parliament and there was “nothing unusual” about this happening during a government term.

A spokesperson for the British prime minister, Rishi Sunak, wished Varadkar well, saying Ireland was “a vital partner” for the UK and that Sunak had “worked well” with him.

Varadkar, who said he had no firm plans for the future but would remain a backbench MP, has an Irish mother and an Indian father and became the country’s youngest taoiseach when he was first elected at the age of 38. He was also the first gay holder of the office.

He has had two spells as prime minister: between 2017 and 2020, and again since December 2022 under a rotation arrangement struck between Fine Gael and Fianna Fáil, the two largest parties in a three-party coalition with the smaller Green party.

Jennifer Bray, a political correspondent for the Irish Times, said that while the resignation might have appeared “dramatic and unexpected”, Fine Gael had been coming under increasing criticism for being out of touch with voters.

“Varadkar’s decision avoids an unseemly heave which, when it has happened in the past, has proven damaging to the party,” she said.