Ulster Unionist leader Robin Swann is to stand down, citing a desire to devote more time to his family.
Mr Swann, who was elected leader in 2017, said he had been reflecting on his position for a number of months.
The move comes after two disappointing electoral performances for the UUP in May.
The party lost the European parliamentary seat it had held for 40 years, trailing in sixth in the May election.
That setback came only weeks after the party lost 13 seats in the local government polls, with casualties including five of its seven seats on Belfast City Council.
Mr Swann has informed party chairman Lord Empey that he will not seek re-election to the post at the next party AGM, which is due to be held in February.
“Over the last number of months I have been reflecting on my position as leader of the Ulster Unionist Party and the impact it has on my role as a husband and a father,” said the North Antrim Assembly Member.
“I have concluded that one is taking up the lion’s share of my time to the detriment of the other. It is unfair to my young family to allow this to continue.
“It has been an honour and a privilege to lead the Ulster Unionist Party and I am grateful for having had the opportunity to do so.”
Mr Swann succeeded Mike Nesbitt as leader. The former TV presenter stood down after a poor electoral showing in the 2017 Assembly election.
Continuing decline
Critics accused Mr Nesbitt of being too liberal, claiming his desire for stronger partnership links with the nationalist SDLP turned off core unionist voters.
Mr Swann is the latest in a line of leaders who have failed to halt the party’s decline.
Once the pre-eminent force in Northern Ireland politics – and a key architect of the 1998 Good Friday Agreement – the UUP has long since been eclipsed by the DUP as the main voice of unionism.
“The Ulster Unionist Party faces its challenges, but I am determined in my remaining time as leader to bring forward the changes required to make it a competitive electoral force once again,” said Mr Swann.
“I believe that it is more important than ever for the Ulster Unionist Party to fight back to help secure and strengthen support for the Union.
“I will continue to serve the party loyally and faithfully as our Assembly Member in North Antrim, an area which has been devastated by recent job losses. There is a huge amount of work to be done as an elected member.
“I want to thank party members for their support over the last number of years.
“I also want to thank my wife Jenny and my children, Freya and Evan, for all the love and support they have given me, and without whom it would not have been possible to do the job I do.” – PA