The DUP will not be nominating a speaker at the first sitting of the new Assembly later today, Sir Jeffrey Donaldson has said.
The move, which is being done in protest against the post-Brexit trading arrangements, means that the Assembly won't be able to function.
It would mean that no ministers could be appointed to the Executive and that no debates could take place in the Assembly. Ministers currently in place can remain in post but their powers would be limited due to the lack of an Executive.
The first sitting of the Assembly is due to being at 12pm today (Friday).
"Today the DUP will not support the election of a speaker in the Assembly,” Sir Jeffrey said in a statement to the News Letter.
“Some parties who just a few months ago were mocking the promise of decisive action from the DUP in relation to the Protocol are the very same parties now feigning surprise and outrage at a political party keeping its promise to the electorate.
"Devolution was restored on the basis of the ‘New Decade, New Approach’ agreement. We have seen delivery of, or significant progress towards nearly every aspect of that document except one.
“That is the UK government’s promise to legislate to respect Northern Ireland’s place within the UK internal market.
“Twenty-eight months since that promise was made and 16 months since it should have been delivered, unionists cannot stand accused of lacking patience."
Sir Jeffrey added that he had "both patience and resolve in equal measure to see the Irish Sea border removed and stable as well as sustainable devolution restored".
He concluded, "Unionist concerns on the Northern Ireland Protocol are not merely some political squabble which is impacting upon Stormont. The protocol is a direct challenge to the principles that have underpinned every agreement reached in Northern Ireland over the last 25 years. It erodes the very foundations that devolution has been built upon.”