The incoming DUP leader has vowed to unite unionism and defeat the Northern Ireland Protocol.
Edwin Poots, who recently recovered from cancer surgery, defeated the DUP’s Westminster leader Sir Jeffrey Donaldson in the battle to replace Arlene Foster, who announced her resignation last month.
The Lagan Valley MLA won by a razor-thin 19 votes to 17 in the poll carried out within the party’s 36-strong electoral college.
In a statement to the media at Stormont, Mr Poots said he will meet Secretary of State Brandon Lewis in Belfast next week over Brexit’s contentious Northern Ireland Protocol.
He also said he intends to be in London later in the week to continue those discussions with the Government.
Mr Poots urged fellow unionists to work with him to oppose the protocol, which has placed new economic barriers between the region and the rest of the UK.
“I want to say this very clearly, I will be a leader in unionism who’ll be reaching out to other leaders in unionism,” he said.
“I want to see unionism working together.
“The Northern Ireland Protocol is proving to be a massive challenge for us and if we are to fight this to ensure that everybody in Northern Ireland is not worse off as a consequence of the protocol, then it’s for us to do that together.
“And I want to ensure that that is the case, that we don’t have the unionist bickering that we’ve had in the past, and I will encourage all unionists to work with me to deliver an end which ensures we set the foundations in this (year) 2021 for another 100 years of Northern Ireland within the United Kingdom.”
Prime Minister Boris Johnson congratulated Mr Poots in a tweet.
“People across the UK are best served when we work together, & I look forward to working with him, @BrandonLewis & the wider Executive as we build back stronger for the people of Northern Ireland,” he added.
Irish premier Micheal Martin also extended his congratulations, and said his door is always open.
It was the first contested leadership vote in the DUP’s 50-year history.
Mr Poots has made clear that he would break with DUP tradition and not appoint himself Stormont first minister if elected party leader.
Wanting to focus “100%” on the leadership, he is set to appoint a party colleague to the role at the head of the powersharing administration at Stormont.
“It is an immense honour and pleasure to stand here today in this position, it is not a position that I expected to be in some weeks ago,” he said in an address at party headquarters in east Belfast.
“However, things can change quite radically.”
Mr Poots added: “I’m looking forward to a positive relationship right across Northern Ireland with my party colleagues and indeed with people from other parties.”
Mr Poots praised the “resilience” of Northern Ireland people through many difficult decades.
“It’s that resilience that we are going to go forward (with) and make Northern Ireland a good place,” he said.
Mrs Foster was ousted after an internal heave by party colleagues unhappy with her leadership and will step down from that role on May 28, and as Stormont First Minister at the end of June.
Mr Poots will be leader designate until Mrs Foster formally stands down.
His election will now go to the party executive for ratification.
The voting by way of secret ballot took place at the party headquarters through Friday afternoon.
Ahead of the vote, Lagan Valley MP Sir Jeffrey and his constituency colleague Mr Poots made final pitches for support in a virtual hustings event on Friday morning.
North Belfast MLA Paula Bradley was also elected the party’s new deputy leader on Friday.
She defeated East Londonderry MP Gregory Campbell by 18 votes to 16.
In his speech, Mr Poots said he wanted to prioritise job creation and improving educational attainment in disadvantaged areas.
He said he wanted to tackle the problems within the region’s health service and address the spiralling treatment waiting lists.
“What we sought to do was to offer the party a choice and I have no regrets about putting my name forward to give the party a clear choice in the decision they had to make,” he said.
“And they have made their choice and I respect that and now the party must consider what that means for our way forward, what it means for the Union that we all cherish and what it means for Northern Ireland, this place that is my home, a place that I love.”
She succeeds Lord Dodds in the role.
“It will be a great honour to serve this great party as deputy leader, I will do so to the very best of my ability, I will give it my all,” said Ms Bradley.
“I will support our leader in any way I can.
“I may be a critical friend at times to our leader, but what more could you expect from me other than that.”