Northern Ireland's newly-formed government can "withstand" last month's shock resignation of the largest unionist party's leader, outgoing Irish Prime Minister Leo Varadkar said on Monday on a visit there.

Jeffrey Donaldson, the former leader of the main pro-UK Democratic Unionist Party (DUP) and one of its best-known politicians, resigned from the post last month after police charged him with historical sex offenses.

Donaldson has said he will be "strenuously contesting" the accusations.

"Events happen in politics," Varadkar told reporters after a meeting of cabinet ministers from the Irish government and members of the devolved UK territory's executive in Armagh, Northern Ireland.

"What's important is that institutions should be able to function through them and withstand any disruption that may occur," he added.

"And that's happened in the past, and I'm sure it can in the future."

Varadkar was on his last official engagement as Irish prime minister following his abrupt announcement last month that he was quitting the role and leadership of the centre-right Fine Gael party.

The political departures have come at a pivotal moment for Northern Ireland, just weeks after the restoration of devolved power-sharing in Belfast following the end of a two-year DUP boycott.

It led to Sinn Fein's Michelle O'Neill making history by becoming the UK territory's first pro-Irish nationalist leader.

The DUP had collapsed power-sharing in 2022 in protest against post-Brexit trade arrangements for Northern Ireland, which shares the UK's only land border with the European Union.

Earlier this year the party struck a deal with the UK government to break the deadlock, paving the way for Stormont to be restored.

The appointment of a Roman Catholic, pro-Irish unity leader in a nation set up as a Protestant-majority state under British rule was hailed as hugely symbolic.

O'Neill on Monday said that it was "business as usual as far as the (Northern Ireland) Executive is concerned" following the DUP's recent tumult.

Meanwhile, Varadkar's resignation announcement on March 20 triggered what pundits called a "political earthquake" in Dublin.

Citing "personal and political reasons" the 45-year-old said he was "not the best person for the job anymore".

He formally hands in his resignation to the Irish president Michael D. Higgins in Dublin later on Monday.

His successor Simon Harris, who also attended the meeting in Armagh, was appointed soon after as the new leader of the governing Fine Gael party following an uncontested election.

Harris, 37, who will be formally elected as the new premier by the Irish parliament on Tuesday, will become Ireland's youngest ever "taoiseach" -- the name for the Irish prime minister and pronounced "tee-shock".

He beats out Varadkar, who was 38 when he took the role in 2017.