DUP Leader Sir Jeffrey Donaldson has confirmed his party will not nominate a speaker when the new Assembly meets on Friday.
In a statement, Sir Jeffrey said the DUP has decided to hold off until it sees what the government intends to do in relation to the Northern Ireland Protocol.
Without a Speaker, the Assembly will be prevented from carrying out business.
"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," said Sir Jeffrey.
"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 and protect Northern Ireland’s place within the UK internal market.
"Twenty-eight months since that promise was made and sixteen months since it should have have been delivered, unionism cannot stand accused of lacking patience.
"I have both patience and resolve in equal measure to see the Irish Sea border removed and stable as well as sustainable devolution restored."
Friday is to be the first meeting of the Assembly since last weeks' Northern Ireland election, which saw Sinn Fein emerge as the largest party for the first time.
The DUP has already indicated that it will not nominate for the position of deputy First Minister, which will prevent the forming of a new Executive, as part of its protest against the Northern Ireland Protocol.
Unionists oppose the post-Brexit treaty because of the economic barriers it creates between Northern Ireland and the rest of the UK.
Sir Jeffrey said his team of MLAs will be at Stormont on Friday to sign the roll.
He will not be in the chamber as he has chosen to retain his position as an MP, despite being elected as an MLA for Lagan Valley a week ago.
Instead, former party MP Emma Little-Pengelly has been co-opted to replace her leader on the Stormont benches.
As the largest party, the new 27 Sinn Fein MLAs will take their position on the benches on the right-hand side of the Speaker's chair for the first time.
It is entitled to nominate its Stormont leader Michelle O'Neill as First Minister, but she will not be able to take up the role without the DUP nominating a deputy First Minister.
Under the rules of the devolved power-sharing administration, both roles are equal and one cannot be in office without the other.
Since last week's election, Ms O'Neill has repeatedly called for the DUP to re-enter the Executive so it can begin to tackle challenges such as the cost-of-living crisis and spiralling hospital waiting lists.
She said on Thursday: "All parties should turn up, all parties should nominate and we should have an Executive up and running.
"There is no reason for that not to happen and it is not acceptable or not good enough that the DUP won't turn up or won't nominate for the position of Speaker or the title of First or deputy First Ministers."
The Stormont sitting comes amid increased tensions between the Westminster government and the EU over the working of the protocol - which forms part of the UK's Withdrawal Agreement with the EU.
Foreign Secretary Liz Truss said the UK will have "no choice but to act" if the EU does not show enough "flexibility" over post-Brexit checks on goods going from Britain to Northern Ireland.
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