Democratic Unionist leader Arlene Foster has accused a senior Irish Government Minister of "aggressive" behaviour on Northern Ireland.
Mrs Foster's remarks about Foreign Affairs Minister Simon Coveney, and specifically his recent comments voicing support for a united Ireland, came as she again heavily criticised the Dublin government for its stance on Brexit.
Relations between the DUP and the Irish Government have deteriorated markedly since Taoiseach Leo Varadkar came into office in the summer.
One of the main bones of contention for the DUP is Dublin's insistence that Northern Ireland should continue to comply with an EU customs framework when the rest of the UK exits the single market and customs union.
Mrs Foster insists that Northern Ireland must be treated the same as the rest of the UK, a message she made clear in her party conference speech in Belfast yesterday.
In an interview with RTÉ, Mrs Foster reiterated her "regret" at the Irish government's position.
But she directed specific criticism at Mr Coveney when challenged about whether the administration's stance on Brexit was motivated by a desire for Irish unity.
"Why then did Simon use this moment in time to talk about his aspiration for a united Ireland in his political lifetime?" she asked.
"I think that's quite aggressive."
As well as Mr Coveney's statement on Irish unity, made to a parliamentary committee in Dublin last week, the DUP leader also referred to his explicit support for a stand-alone Irish language Act for Northern Ireland, the key sticking point between the DUP and Sinn Féin in talks to restore powersharing at Stormont.
Noting commentary around the DUP's Westminster deal with the Conservative Party, and criticism that the UK government was undermining its stated impartiality in Northern Ireland as a result, Mrs Foster suggested the Irish Government was not adverse to making partial statements itself.
"Simon thinks it's OK to speak about an Irish language Act and it's quite OK to say: 'I want a united Ireland and it's going to happen in my political lifetime', so it goes both ways," she said.
Mr Coveney replaced Charlie Flanagan as Foreign Affairs Minister when Mr Varadkar succeeded Enda Kenny as Taoiseach.
Mrs Foster accused Fine Gael's new generation of leaders of indulging in megaphone diplomacy.
"Some of the rhetoric coming from Dublin recently has been of a nature that actually could bring about self harm to the Republic," she said of the Brexit talks.
"What we should be doing is actually working together to find a way forward, but since this administration came into office, since Leo took over, and Simon became the foreign minister, there hasn't been that same engagement that we had with Enda and Charlie.
"And I regret that because it I think we should be working together because we are on this island."
Addressing the Oireachtas committee on the implementation of the Good Friday Agreement last Thursday, Mr Coveney told members: "I am a constitutional nationalist, I would like to see a united Ireland in my lifetime.
"If possible, in my political lifetime."