Leo Varadkar on Wednesday announced that he was stepping down as Ireland's prime minister and leader of the Fine Gael party in the governing coalition, citing "personal and political" reasons.

Pundits called the move, just 10 weeks before Ireland holds European parliament and local elections, a "political earthquake". The country must also hold a general election within a year.

Deputy Prime Minister Micheal Martin, leader of the Fianna Fail coalition partner, said the announcement was "unexpected" but added that he expects the government to run its full term.

An emotional Varadkar, 45, said he felt he was no longer the "best person" to lead the country. 

"I believe this government can be re-elected," Varadkar said in a statement read on the steps of Government Buildings in the Irish capital, surrounded by his Fine Gael cabinet colleagues.

"I believe a new Taoiseach (prime minister) 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.

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

"I am resigning the presidency and leadership of Fine Gael and will resign as Taoiseach as soon as my successor is able to take up that office," Varadkar told reporters.

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

Earlier this month Varadkar was widely blamed for a twin defeat, including the biggest ever referendum loss by a government, on proposals to reform references to women, the family and care in the Irish constitution.

Varadkar said his centre-right Fine Gael party will have a leadership contest, and that he will remain as premier until the new leader is elected, after parliament returns from recess next month.