Stormont's First Minister Arlene Foster will face a vote of no confidence in her leadership at the devolved Assembly later today as the fall out from a botched green energy scheme intensifies.
She leads the Democratic Unionists who share power with Sinn Fein at the Northern Ireland Assembly.
Deputy First Minister Martin McGuinness has called on her to step aside while what critics claim is a scandal is investigated.
A generous scheme which was designed to encourage businesses to switch from burning fossil fuels is now predicted to cost the public purse an extra £400 million after inadequate cost controls.
Mrs Foster's role in establishing it and in the period before it was shut down is under intense scrutiny.
The ministerial exclusion motion was tabled by the nationalist Social Democratic and Labour Party (SDLP) with support from the Ulster Unionists, cross-community Alliance Party, Green Party, Traditional Unionist Voice and left wing People Before Profit.
SDLP leader Colum Eastwood said: "With each passing hour, credibility drains from the First Minister and confidence drains from the institutions.
"The only way to decisively address the situation is for Arlene Foster to follow the precedent set by her immediate predecessor and stand aside as First Minister pending a full inquiry."
The DUP can use a special parliamentary procedure to prevent the motion's passage even if Sinn Fein supports it.
Mr Eastwood added: "If the First Minister refuses to stand aside then the Assembly must act to restore public confidence by removing Arlene Foster from office.
"The SDLP ministerial exclusion motion is designed to remove the First Minister for a period of six months to allow a full inquiry to get under way.
"The intervention of the deputy First Minister at the end of last week is welcome and its only logical conclusion must be that Sinn Fein back the SDLP ministerial exclusion motion. That's what their electorate are demanding. It's what we expect."
The row threatening the peace-building institutions has erupted over the controversial energy scheme - set up by Mrs Foster - which paid out subsidies well in excess of the costs of buying renewable fuel.
Claims of widespread abuse include a farmer allegedly set to pocket around £1 million in the next 20 years for heating an empty shed.
The "cash for ash" scandal reached fever pitch when former economy minister Jonathan Bell broke ranks to level a series of explosive claims against his leader and party advisers.
In an extraordinary TV interview, a tearful Mr Bell said God told him to come clean as he claimed a "highly agitated and angry" Mrs Foster demanded he keep the Renewable Heat Incentive open for an extra fortnight despite its huge losses.
Mr Bell was suspended by the party over the weekend.