PARTY special advisers "were in charge" following the re-establishment of the assembly in 2007, a senior civil servant has claimed.
Dr Andrew McCormick told the Renewable Heat Incentive (RHI) inquiry that it had been clear to civil servants as early as 2007 that advisers were in control at Stormont.
Dr McCormick, who has appeared before the inquiry several times, was head of the enterprise department when serious issues with the botched RHI scheme began to emerge.
The flawed green energy scheme is expected to cost taxpayers up to £490 million.
On the final day of oral hearings yesterday, chairman Sir Patrick Coghlin questioned why Dr McCormick did not ask for copies of emails between DUP special advisers which included allegations party adviser Andrew Crawford had delayed cost controls.
"I would have been rebuffed," the civil servant said. He added: "The reality of what we'd got used to was that they were in charge".
He said that position was clear from 2007.
Dr McCormick told the inquiry he was personally asked by senior DUP adviser Timothy Johnston, now party chairman, to search the RHI database for relatives of fellow adviser Dr Crawford.
He said Mr Johnston gave him the relatives' names.
Mr Crawford's brother James and cousins Richard and John Crawford were recipients of the scheme.
Dr McCormick said when he met Mr Crawford at a business dinner in October 2016, the "very relaxed and smiling" former adviser said he believed the RHI scheme would be funded from the Treasury, not the Stormont budget, and "we could fill our boots".
The senior civil servant, who became visibly emotional as he completed his evidence, said he felt "ashamed personally" for issues with RHI and apologised "for the failings of the civil service in this case".
However, he added that DUP special advisers knew about potential abuse of the scheme "and didn't tell us".
He added: "There are a lot of things that are down to the civil service and we have to accept responsibility... but the Spad involvement is much clearer and starker..."
The inquiry also heard from former civil service head Sir Malcolm McKibbin who said he was "surprised and disappointed" that the appointment of special advisers did not adhere to the proper code.
Several witnesses have already told the inquiry that DUP Spads were appointed by the party, not the minister, in contravention of the code of conduct.
Sir Malcolm said if power-sharing is restored civil servants should ask for written evidence of how a Spad has been chosen.
"They are meant to keep written evidence of how they've followed the procedures," he said.
The inquiry's oral hearings ended yesterday following 111 days of evidence.
Inquiry counsel David Scoffield said the inquiry will continue to gather evidence.
Further witness statements will be published and legal sessions will be held in mid-December.
