SINN Féin has confirmed it will not renominate a deputy first minister before today's deadline – dashing any remaining hopes of saving Stormont from collapse.
The assembly is set for a day of political drama as it reconvenes for the first time following the row sparked by the 'cash for ash' scandal.
A week ago Martin McGuinness resigned as deputy first minister in protest over the DUP's handling of the Renewable Heat Incentive (RHI) controversy.
The political crisis is set to reach fever pitch at 5pm – the deadline for Sinn Féin to nominate a replacement for Mr McGuinness.
But in a statement on Sunday night, health minister Michelle O'Neill said Sinn Féin would not be renominating and repeated the party's calls for a fresh election.
"Sinn Féin will not be nominating for the position of deputy first minister and the agreements mean that the people must now have their say," the Mid Ulster MLA said.
"We all, including the other parties and the two governments, have a role to play to rebuild confidence in the political process and institutions that deliver for all our people and operate on the basis of equality and respect.
"Sinn Féin remains committed to dialogue. This will require a step change from the governments and other parties. There can be no return to the status quo at Stormont.
"At this time there is no basis for credible negotiations to reinstate the institutions and we now must move to an election."
In a packed day of assembly business, MLAs are also set to vote on emergency proposals by DUP economy minister Simon Hamilton attempting to claw back some of the RHI overspend.
Finance minister Máirtín Ó Muilleoir said on Sunday that his department would "robustly" test the proposals being put forward by Mr Hamilton.
However, he said there was no "zero cost solution" to the £490 million overspend problem.
The Sinn Féin South Belfast MLA also repeated calls for the beneficiaries of the RHI scheme to be published and urged an early election.
The assembly speaker, the DUP's Robin Newton, also faces a motion of no confidence later on Monday.
He has faced criticism in recent weeks over his handling of assembly debates surrounding the RHI scandal and east Belfast organisation Charter NI.
SDLP North Belfast MLA Nichola Mallon said the speaker must step aside in an attempt to rebuild confidence in the assembly.
"The Office of the Speaker is a source of authority in the Northern Ireland Assembly, and should be impartial. However, Mr Newton has undermined that authority on various occasions since he took up his role as speaker," she said.
The earliest possible election date is five weeks from today and there would also be up to three weeks of negotiations following that to form a new executive.
Mr McGuinness's resignation automatically removed DUP leader Arlene Foster from her position as first minister – as executive structures dictate one cannot govern without the other.
Doubts remain over whether he will stand for an assembly seat due to ill-health.
