He will remain as an MP in London.
DUP Leader Jeffrey Donaldson's resigned from the Stormont Assembly, but will stay on as an MP in London.
Emma Little Pengelly has been co-opted to fill the vacant seat in Lagan Valley.
The DUP says it won't form a joint government with Sinn Fein until its concerns over the Northern Ireland Brexit protocol are addressed.
Meanwhile, the British Foreign Secretary earlier said there would be "no choice but to act" if no agreement can be reached to change the post-Brexit trade deal.
EU Commission Vice President Maros Sefcovic insists there will be no re-negotiation:

Mother Of Man Accused Of Limerick Woman's Murder Appears In Court For Withholding Information From Police
Kildare TD Brings Forward Motion To Reverse Public Transport Price Hikes
Highest Rate Of Inflation Recored Since 2023, According To CSO
Public Sector Strike Called Off After Pay Deal Agreed
Man (52) Found Guilty Of Murdering 89-Year-Old Woman In Tipperary
Dublin City Traffic Restrictions Begin Ahead Of Major Meetings Of World Leaders
Public Sector Talks To Resume At WRC Today, Amid Looming Strikes
Gardaí Call Off Work-To-Rule At Last Minute