Irish premier Micheal Martin said Thursday that Boris Johnson's resignation as Conservative leader, paving the way for a new UK prime minister, was "an opportunity" to reset fraught relations.
Martin added ties between Dublin and London had been "strained and challenged in recent times", not least because of clashes over special post-Brexit trade arrangements in British-run Northern Ireland.
Johnson quit as Tory leader following a series of scandals and an exodus of cabinet ministers and will be replaced once his party's MPs, and then eventually its members, elect a successor.
"We have now an opportunity to return to the true spirit of partnership and mutual respect that is needed to underpin the gains of the Good Friday Agreement," Martin said in a statement.
The 1998 peace accords ended decades of bloodshed over British rule in Northern Ireland but has been increasingly strained by Brexit.
"Our joint responsibilities concerning stewardship of the Good Friday Agreement, as well as nurturing broader bilateral relations between us, require us to work together in a spirit of respect, trust and partnership," Martin added.
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"That is more important than ever today and I would once again urge a pulling back from unilateral action, whether that be on dealing with the legacy of the past, human rights, or the Northern Ireland Protocol."
The UK agreed the protocol with the European Union, keeping Northern Ireland in its single market and customs union, alongside its wider Brexit withdrawal deal with the bloc.
But last month the UK government unveiled legislation to unilaterally scrap parts of the Northern Irish pact.
The move comes amid political stalemate in the province after unionist parties, which argue it is threatening their place within the UK, refused to rejoin power-sharing structures following recent elections unless it is overhauled.
On Thursday, Northern Ireland's first minister-elect, Michelle O'Neill, of Irish nationalists Sinn Fein -- which won a historic first victory in the May ballot -- accused Johnson of trying to "sabotage" peace there.
"It has been an utter absurdity that the people here have been subjected to Boris Johnson for any length of time," she said on Twitter ahead of his resignation announcement.
"He is a figure of absolute disrepute. Anyone who tries to sabotage our peace agreements, a quarter century of progress and our shared future is truly no friend of ours."
Johnson, who plans to remain in post for several months until his successor is chosen, announced a new secretary of state for Northern Ireland on Thursday.
The newly appointed minister, Shailesh Vara, enters the role after predecessor Brandon Lewis resigned -- one of more than 50 members of the UK government to quit in the ultimately successful bid to oust Johnson.
Vara previously served in the UK's Northern Ireland Office as a junior minister in 2018.