Northern Ireland Finance Minister Máirtín Ó Muilleoir has dismissed a plan to deal with the renewable heating scandal as "nothing but a sticking plaster".
The Sinn Féin minister rubbished claims by DUP Economy Minister Simon Hamilton that he and First Minister Arlene Foster had come up with a solution to reduce the Renewable Heat Incentive Scheme overspend from approximately £490 million to "effectively zero".
Mr Ó Muilleoir also warned that the political institutions will collapse unless the First Minister steps aside to facilitate an independent investigation into the scandal.
Following a meeting with Mr Hamilton, Mr Ó Muilleoir said he was "bitterly disappointed" by the proposal outlined to him.
"I still haven't seen a plan, there is no plan. When I went to the meeting, there was no plan ready for me and, in fact, I am told that rather than a solution, we now have an interim solution, a sticking plaster.
"In the strongest terms possible, I have said to the Economy Minister, 'This isn't the time for sticking plasters, the public is crying out for a solution'. Really I think they need to move to bring forward a comprehensive plan," said Mr Ó Muilleoir.
He added: "I think it is a grave mistake to go forward with an interim solution. It is a grave mistake to apply a sticking plaster to this gaping wound. We need a comprehensive plan on how to bring the debacle to a close.
"There has been no real attempt, in my view, to try and get a solution to this dreadful waste of public money until the Spotlight programme."
He also said that he was not confident that the overspend could be reduced to zero.
"It is not a no-cost solution. There will be costs in bringing forward a monitoring of the system, there will be costs involved, at very least to the end of this year, because they are talking about the solution not coming in until the new financial year. And of course the big question is, does it blow up again? No doubt it will be challenged and hundreds of thousands of pounds spent defending it."
Mr Ó Muilleoir insisted that the First Minister must step aside.
"By refusing to step aside she has sounded the death knell for the Assembly, the Executive and the institutions.
"The only key to release us is Arlene Foster. To do that she would have to do the right thing by the community and step aside.
"In the history of the state there has never been as dreadful a financial disaster as this one. If she doesn't stand aside, I think there is no future for these institutions," he said.
All rival parties at Stormont have demanded Ms Foster stand aside while her role in the affair is investigated.
Ms Foster oversaw the inception of the RHI scheme during her time as economy minister.
She has steadfastly refused to step aside and has claimed some of those calling for her head are motivated by misogyny.
The state-funded RHI was supposed to offer a proportion of the cost businesses had to pay to run eco-friendly boilers, but the subsidy tariffs were set too high, and without a cap, so it ended up paying out significantly more than the price of fuel.
This enabled applicants to "burn to earn" - getting free heat and making a profit as they did it.
Claims of widespread abuse include a farmer allegedly set to pocket around £1 million in the next two decades for heating an empty shed.
Senior members of Sinn Féin have warned they will exercise their power to collapse the power-sharing Executive if Ms Foster does not temporarily stand down to facilitate a probe.
If the party follows through with that threat Northern Ireland will be facing a snap Assembly election, less than a year after the last one.
It was originally envisaged that the Treasury would foot the bill for the RHI, but the costs spiralled well beyond London's financial commitment.
The total RHI spend in Northern Ireland is estimated at $1,150 million over the next 20 years.
The Treasury is set to cover $660 million of that, with Stormont landed with the remaining $490 million.
DUP member labels crisis an 'omnishambles'
A former Assembly colleague of Ms Foster has broken ranks to heavily criticise her handling of the botched green energy scheme.
Democratic Unionist David McIlveen, an ex-Assembly member, said his party leader had "seriously misjudged the public anger" over an initiative.
He branded the scandal an "omnishambles" and claimed an internal storm was brewing within the ranks of the party about Ms Foster's leadership.
Mr McIlveen questioned whether Ms Foster had become an "electoral liability" for the party and expressed doubt she would be leader in the long term.
"Whilst the view in public is that 'Arlene's team' are as loyal and happy as ever, the reality in private is something very different," he said.
Writing in the News Letter, he added: "Does a party obsessed with winning elections want to move forward with a leader who appears incapable of facing up to their mistakes, and attacks on a personal level their critics even if they are members of their own party?
"I think the answer to that question is fairly obvious and therefore believe it is highly unlikely that 2020 Westminster elections will be fought under the existing DUP leadership."