A senior civil servant has said he "can't satisfactorily explain" why the botched Renewable Heat Incentive (RHI) scheme was never reviewed.
Department of Finance permanent secretary David Sterling was head of the Department of Enterprise, Trade and Investment (Deti) for much of the time the renewable energy scheme operated.
He said his department is examining ways to minimise the £1bn-plus commitment to RHI, which is expected to put significant pressure on the Executive's budget over the decades ahead.
Dubbed "the biggest scandal since devolution began", the RHI was designed to wean businesses off fossil fuels, with uptake among the north's poultry farmers especially strong.
However, a report from the Audit Office in July identified "serious systematic failings" in the non-domestic element of the initiative.
Unlike a corresponding scheme Britain, the amount of money that could be claimed was not capped, which is thought to have led to many businesses burning more heat than they required just to make money.
Mr Sterling, who told the assembly's Public Accounts Committee he was constrained in his responses due to a fact-finding review at the Department for Economy, said ahead of his departure from Deti in July 2014 there had been no review of the scheme, which he conceded would have likely flagged up its shortcomings.
"I accept that a review did not take place in my time – I accept that in the business case it was said a review would take place in early 2014," he told MLAs.
"I can't satisfactorily explain why the review didn't take place."
Arlene Foster talking about the RHI scheme in October:
Mr Sterling was criticised by Sinn Féin's Declan Kearney for pleading ignorance or citing Deti's fact-finding exercise for preventing him from answering certain questions.
"Therefore, you're fettered in your ability to analyse this situation and give us a view in what has gone wrong," the South Antrim MLA said.
Mr Sterling said efforts were being made to reduce the executive's long-term commitment to the scheme.
He said "everything has to be done to reduce the budgetary pressure going forward".
"We have to stop the exposure to the block (grant)," the senior civil servant said.
Last week, The Irish News revealed that an unwritten convention means First Minister Arlene Foster will not be questioned about her oversight of the RHI.
The DUP leader was in charge of the Deti portfolio for much of the time the scheme operated but has rejected any responsibility for its shortcomings, saying ministers "do not get to see that level of detail".
