The SDLP leader Colum Eastwood has called on DUP members to intervene and force Arlene Foster's resignation over the so-called 'cash for ash' scandal.
Citing remarks by Ms Foster in which she accused her rivals of misogyny, Mr Eastwood said: "Since this scandal broke, the DUP have used every weapon in their political arsenal.
"They have tried the orange card, the scapegoat card, the misogyny card and everything else in between. The one approach they have failed to adopt is showing a bit of humility and honesty."
He added: "It is time the DUP now accepted that each and all of their tactics have failed. We are long since past the point of no return for Arlene Foster and this crisis has gone on far too long. The DUP have run out of road."
"It is now decision time for senior members of the DUP - party loyalty must have its limits. No one individual should be bigger than their party and no one individual can be bigger than the privileged office they occupy," said Mr Eastwood.
Meanwhile, Alliance Party leader Naomi Long said the DUP and Sinn Féin needed to "get off their high horses" and not concoct a deal that "compromises openness and accountability".
"People won't accept a deal between the DUP and Sinn Féin over this scandal," she said.
"Openness and accountability are not something up for trading. We need to see a proper public inquiry - anything short will leave lingering suspicions. Public confidence requires those against whom there are major allegations to at least temporarily step aside."
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, 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 £1m in the next two decades for heating an empty shed.
Ulster Unionist MLA Steve Aiken asked why steps to reduce the RHI spend were only being devised now, rather than when a critical report by auditors was published last summer.
He noted that in July 2015, current Economy Minister Simon Hamilton said options to mitigate the costs were being actively considered.
"So the question is, six months later, what were the options that the minister was actively considering at the time of the audit office report, and what has become of these options?" Mr Aiken asked.
"It is time to end this nonsense. The minister should publish all the options that have been under 'active' consideration by him, both then and now."