Former DUP MP Emma Little Pengelly has been co-opted to replace her leader Sir Jeffrey Donaldson as an Assembly member for Lagan Valley.
Sir Jeffrey won the seat days ago after contesting the Assembly election.
However, he revealed earlier this week that he intends to remain at Westminster as an MP until issues with the Northern Ireland Protocol are resolved.
The Electoral Office for Northern Ireland website states: "Emma Little Pengelly has been returned as an MLA to fill the vacancy arising from the resignation of The Rt Hon Sir Jeffrey Donaldson MP."
Sir Jeffrey Donaldson said: "The people of Lagan Valley and throughout Northern Ireland gave me a mandate, based on a commitment that we will not nominate Ministers to a new Northern Ireland Executive until the issues flowing from the Northern Ireland Protocol are satisfactorily dealt with and Stormont is able to return on a stable and durable basis.
"I will continue as the Member of Parliament for Lagan Valley until the Protocol issues are resolved. It is important that the Protocol is replaced with new arrangements that respect Northern Ireland’s place within the United Kingdom and as the leader of Unionism that work is in London.
"In the interim period I have asked Mrs Emma Little Pengelly to represent people in the Lagan Valley constituency at the Northern Ireland Assembly. Emma will be a first class advocate for people and will work hard to advance the issues that matter to everyone in Lagan Valley. Emma is again stepping forward to help articulate the cause of the Union and I welcome her return to our ranks.”
Emma Little Pengelly said: “Sir Jeffrey Donaldson has an important task to complete in addressing the continued problem of the Protocol, which is causing untold damage to our economy and to political stability in Northern Ireland. This requires him to be in London and working closely with the UK Government.
"Consequently I have agreed to fill his seat in Lagan Valley, at this time, both to support this work and to ensure a continued high level of support and service to the constituents of Lagan Valley.
"It is a privilege to be asked to fulfil this role at this important time for Unionism and for Northern Ireland. While Sir Jeffrey focuses on that immediate task, I look forward to serving the people of Lagan Valley with passion and commitment.”
Earlier, DUP leader Sir Jeffrey Donaldson confirmed his team of MLAs will attend Stormont on Friday to sign the roll.
However, he has yet to make a decision on if his party will nominate a speaker, saying that will come just moments before all MLAs are set to join together for the first time since the election.
"We are committed to making the political institutions work but we're also clear that we need to see decisive action by the government," he said.
Asked whether his party will nominate a speaker, he said: "Our Assembly group will meet and come to final decisions in all of this tomorrow morning.
"The Assembly meets tomorrow morning and parliamentary protocol determines that the first people to know are the people who actually sit in an Assembly, therefore we will make our position clear on this.
"We recognise that these issues need to be dealt with. As a party we have been decisive, we have made our position clear and will continue to do so."
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