Arlene Foster says heat scheme flaws are her 'deepest political regret'
Northern Ireland's first minister has said she is sorry that the Renewable Heat Incentive (RHI) scheme "did not contain cost control measures".
She also said there were "fundamental flaws in its design."
Arlene Foster told MLAs: "This is the deepest political regret of my time in this house."
"As minister, I accept responsibility for the work of the department during my time at the Department of Enterprise, Trade and Investment."
Arlene Foster was speaking in the chamber to DUP MLAs, only after all the other assembly members left in protest.
"Once again, and for avoidance of doubt, I believe it is right and proper that I answer to this assembly for my role in the RHI scheme," she said.
"Not for one moment do I seek to shirk or avoid that responsibility, but if we are to learn lessons from this entire experience, it is essential that we know exactly where things went wrong."
She told the assembly: "I can also confirm that the DUP party officers took no interest or role in the question of the RHI.
"Therefore, regardless of what, if anything, was said in relation to the role of the party, no-one had any authority to instruct the Deti minister to do anything.
"I would add that there is no evidence whatsoever of Mr (Jonathan) Bell raising any concerns with the first minister if he felt that he was being pressurised.
"Let me make it absolutely clear, any suggestion that the enterprise minister was instructed to delay the changes to the RHI scheme is totally without foundation. "
The first minster then turned to allegations made to BBC Northern Ireland's Stephen Nolan last week by Jonathan Bell.
Mrs Foster said "The former Deti minister claims that he made a decision to amend the RHI scheme, but that he was overruled by special advisors.
"Since last week, I have specifically investigated this claim.
"The evidence is clear. The only decision taken by the minister was in early September to amend the scheme in November.
"The minister was not subsequently overruled by special advisors and I am clear that whatever representations may have been made by anyone on this issue, it was not not being done with the authority of the party.
"I understand from Minister (Simon) Hamilton that the permanent secretary recalls being told at the time that some in the party wanted the scheme kept open.
"He was unaware of the source of this suggestion, but believes it may have been based on the erroneous but widespread view at the time that because the scheme was AME funded that it was possible to maximise take-up without creating a problem.
"I have checked and confirmed that no minister made any such request or took any interest in the decision taken in September 2015.
"The DUP party officers took no interest in this issue and gave no instructions. It is therefore clear that whatever the belief, the DUP did not ask the Deti minister to extend the scheme."
Mrs Foster also confirmed that plans to recoup some of the RHI money are being worked on and she said she supported an independent investigation.
She told the assembly: "I also want to make it clear that I support the need for an independent investigation, free from partisan political interference, to establish the facts around the RHI scheme.
"I believe that the conclusions of any investigation must be made public and that any investigation must be conducted speedily to assist in the process of building public confidence.
"I have been working to reach agreement with officials and others on the precise details of such an investigation over the last number of days.
"I hope that this can be resolved in the next few days."
She added: "Minister Hamilton plans to make a statement to the assembly as soon as possible in the New Year. The hope and intent is to reduce significantly the cost of the scheme to the executive's budget, but the details are still subject to considerable further work. "