Incoming DUP leader Jeffrey Donaldson is to speak to UK prime minister Boris Johnson about unionist opposition to the Northern Ireland protocol "at the earliest opportunity".
In a statement issued after he was named as the party’s next leader on Tuesday, Mr Donaldson said he would “emphasise that it is not realistic to expect stability when every unionist representative in the devolved institutions opposes the Northern Ireland Protocol”.
He called on the UK government to “step up and deal with the protocol”, saying it and those who “claim to be protectors of peace and stability” must do so in a manner “which respects the constitutional and economic integrity of the United Kingdom”.
However Mr Donaldson also stressed of the need for reconciliation and healing within unionism and the wider community, and articulated his commitment to the powersharing Assembly at Stormont.
“The Northern Ireland Assembly is the place where every element of our society is represented. The coalition government is unwieldy, but it ensures every voice is heard,” Mr Donaldson said. “Such partnership is how we should move forward. It must be based on respect for each other’s mandate.”
The Sinn Féin leader, Mary Lou McDonald, said on social media that she had spoken to Mr Donaldson, and they would meet early next week.
Minister for Foreign Affairs Simon Coveney tweeted his congratulations to Mr Donaldson, saying: “I genuinely wish u well & look forward to working with you on the many challenges that lie ahead. Respect.”
The Northern Secretary, Brandon Lewis, also congratulated him, and said he looked forward “to continuing to work with him and the whole Northern Ireland Executive, ensuring we deliver on the shared interests of all the people of Northern Ireland”.
A Government spokesperson in Dublin said it “looks forward to early meeting” with Mr Donaldson.
Nominations for the post of DUP leader closed at midday on Tuesday, and the party chairman, Lord Morrow, confirmed shortly afterwards that Mr Donaldson had been the only candidate.
"Following the completion of our party process Sir Jeffrey Donaldson MP will be the next leader of the Democratic Unionist Party, " he said.
His selection will go before a meeting of the party’s electoral college of 28 Assembly members and eight MPs on Saturday, and will then be ratified by a meeting of its central executive committee next week.
It is understood the party wants to complete the process as soon as possible in order to move on from the damaging internal split occasioned by the ousting of Arlene Foster and the leadership election narrowly won by the outgoing leader Edwin Poots.
“The last number of weeks has been difficult for the party and mistakes have been made,” Lord Morrow said. “Now is the time to move forward in a spirit of humility.”
The process to find a new party leader was initiated on Thursday when Mr Poots resigned after only three weeks in office.
He lost the support of his party after he went ahead with the nomination of his close ally Paul Givan as Northern Ireland's First Minister on the basis of a deal brokered by the Northern Secretary on Irish language and other cultural legislation.
The length of Mr Givan’s tenure as First Minister remains unclear, but speaking to reporters on Tuesday he gave Mr Donaldson his backing.
“Jeffrey has made clear that he does want to come back to Stormont in due course and wants to be First Minister, and Jeffrey will make an exceptional First Minister, nobody doubts that.”
There has been speculation that Mr Givan could remain in post in the short-term, or that an interim First Minister could be appointed while Mr Donaldson stands down as an MP – triggering a byelection in the Lagan Valley constituency – and seeks an Assembly seat.
A senior DUP source told The Irish Times that the former junior minister Gordon Lyons could be interim First Minister, and that Mr Donaldson had spoken to Mr Poots and it was expected that the outgoing DUP leader would remain in post as Minister for Agriculture.