Outgoing Ulster Unionist Party (UUP) leader Doug Beattie always sought to act in the best interests of Northern Ireland, the Secretary of State has said.

Mr Beattie quit on Monday, citing “irreconcilable differences” with party officers.

Senior political figures have paid tribute to his leadership and constructive approach to relations with other parties.

Northern Ireland Secretary Hilary Benn thanked Mr Beattie for his “commendable leadership”.

In a statement, Mr Benn said: “It is clear that he has always sought to act in NI’s best interests and I know he will continue to do so.

“I look forward to working closely with his successor.”

DUP leader Gavin Robinson said that while he differed from Mr Beattie on tactics, there was “no doubt that Doug is a committed Unionist”.

Mr Robinson criticised UUP electoral strategy and said divisions within unionism had handed seats to non-unionists.

He added: “Top of my priorities for the new leader will be discussions about how we maximise the pro-Union vote in future elections.”

Sinn Fein’s vice president Michelle O’Neill said the party will take a “constructive approach” with the new leader of the UUP.

Ms O’Neill said: “I want to wish Doug Beattie and his family well as he announces today that he will step down as leader of the UUP.

“We have worked constructively since he became leader of his party, including during the restoration of the Executive and institutions at the beginning of this year.”

The First Minister added: “I will continue this constructive approach with the new leader of the UUP when they take up post.

“Sinn Fein will continue to work together with all parties in the Executive and Assembly to ensure we deliver for all.”

Deputy First Minister Emma Little-Pengelly said unionists must move forward, as she wished Mr Beattie well for the future.

The DUP MLA for Lagan Valley said: “Unionism moves forward into a new chapter, one in which we must seize the opportunity to secure and strengthen our Union, together.”

UUP MLA and Health Minister Mike Nesbitt said the announcement came as a “shock”, adding: “I’ve been very supportive of him during the years, and I’m very sorry to see him step down.”

Mr Nesbitt, who is also a former UUP leader, said the party faces a challenge in addressing internal matters.

He told RTE radio he had not given the possibility of returning to leadership a “millisecond’s thought”.

Irish premier Simon Harris expressed well wishes to Mr Beattie.

In a social media post, he said: “I would like to wish Doug Beattie and his family well as he steps down as UUP leader.

“Doug has been a responsible and constructive leader in Northern Ireland during times of great challenge in recent years.

“On a personal level, I have always found him to be engaging and decent.”

Irish deputy premier Micheal Martin said Mr Beattie led his party through “numerous challenges”.

Mr Martin said: “I’ve always appreciated his emphasis on making politics work & the constructive relationship we built.

“I know he will continue to lead by example whatever the future holds.

“A strong relationship between this government and political leaders in Northern Ireland is vital – I look forward to building the same ties with Doug’s successor.”

SDLP leader Colum Eastwood paid tribute to Mr Beattie’s dedication to serving the people of Northern Ireland.

He said: “Doug and I have different politics but I’ve always admired his candour and commitment to working together in the interests of the people we represent.

“I know this won’t be the end of his political contribution but hope he enjoys some more time to spend with his loving family.”

Alliance leader Naomi Long wished Mr Beattie well for the future, and deputy leader Dr Stephen Farry added: “He will no doubt continue to make a significant contribution to politics and public life.”

Ireland’s former deputy premier Simon Coveney said he was “sorry” to see Mr Beattie step down.

Mr Coveney, who was Irish foreign affairs minister during Brexit negotiations between the UK and the EU, said: “I always found Doug to be fair, tough when needed, reasonable and positive.

“Of course we didn’t agree on everything, but Doug was someone I trusted and respected as a strong unionist leader.”