Northern Ireland assembly politicians walked out of the Stormont parliament ahead of a statement by the First Minister on a botched energy scheme.
Assembly members from opposition parties said Arlene Foster had no authority to give the statement on the scheme, which could cost the taxpayer £400m, because it was not backed by deputy first minister Martin McGuinness.
The Sinn Fein politician said he would not back the statement of the joint leader of the power-sharing executive because her proposal for an investigation into the scheme she introduced as Enterprise Minister does not go far enough.
The devolved assembly at Stormont had been recalled from Christmas recess over what opposition parties have described as “the biggest public finance scandal since devolution”.
But her statement was delayed by around 30 minutes by the walkout after Mr McGuinness called for her to stand down.
Sky News Northern Ireland Correspondent David Blevins said it was “effectively the collapse of the devolved government in Northern Ireland”.
Mrs Foster was forced to make her statement only to members of her own Democratic Unionist Party, telling them that the lack of cost controls on the scheme, which became known as cash for ash, was her “biggest political regret”.
She said that she had no idea of the overspend on the scheme.
Members of opposition parties had been expected to move a motion of no confidence in the First Minister, however, it did not get to that point.
Mrs Foster had faced down opponents, dismissing the vote as a “political stunt” with “no value”.
She said: “It can’t compel me to do anything and it has only been brought about to try and add to the hyperbole that has come forward from the opposition parties.
“Well I have news for them. I am not resigning.
“I have a job to do and I intend to get on with that job because the mark of a politician is not what he or she does in good times. It’s what he or she does when there are challenges in front.”
The Renewable Heat Incentive, launched by Mrs Foster when she was Enterprise Minister, offered subsidies to businesses switching to greener fuel.
When some were found to be heating empty warehouses, it emerged a lack of cost controls meant the more they burned, the more they earned from the public purse.
For every £1 they spent, participants received £1.60 in subsidies, resulting in the scheme overspending by an estimated £400m.
Sinn Fein, which shares power with Mrs Foster’s Democratic Unionist Party, want Mrs Foster to stand aside as First Minister while the scandal is properly investigated.
Mr McGuinness said: “It is my firm belief the only way to establish the truth of what has occurred and to begin to restore public faith in the institutions is for an independent, time-framed and robust investigation to take place.
“The First Minister should stand aside to allow this. There is also an urgent need to minimise the cost of the scheme to the public purse.”