In the last elections in 2020, Fine Gael finished behind Sinn Fein and Fianna Fail.

His predecessor, Micheál Martin, the leader of Fianna Fail and deputy prime minister, said: “I was surprised. I didn’t expect it at all.”

The announcement took a lot of courage, he added.

Mr Varadkar suffered a defeat in a referendum earlier this month held to remove sexist language about women’s duties in the home from the Irish Constitution.

His resignation came after the first meeting of the Cabinet held after the double referendum, in which voters also refused to expand the constitutional definition of the family beyond married couples.

Paschal Donohoe, Simon Harris and Heather Humphreys are among the ministers being considered to replace Mr Varadkar.

Mr Donohoe is minister for public expenditure and also president of the eurogroup of finance ministers in Brussels.

Mr Harris, 37, is education minister, while Ms Humphreys is a minister for rural development, who is the only Presbyterian in the Irish parliament and has described herself as a protestant, Ulsterwoman and proud Irish republican.

Mr Varadkar’s first stint as leader was dominated by Brexit, which Dublin saw as a threat to its place in the EU’s Single Market because of the invisible land border with Northern Ireland.

Rishi Sunak praised Mr Varadkar for his “dedicated service” after the Taoiseach announced his plan to step down.