DUP special advisers (Spads) tried to frustrate changes to the Renewable Heat Incentive (RHI) scheme while party officers hijacked a decision by the minister on its closure, a senior civil servant has claimed.
John Mills, the former head of the energy division at the Department of Enterprise, Trade and Investment (Deti), made the claim about former spads Timothy Cairns and Andrew Crawford during yesterday's hearing of the public inquiry into the botched green energy scheme.
Mr Mills also said he had told the department's permanent secretary, Andrew McCormick, that there "should be a leak inquiry" after it became clear there had been a spike in RHI applications just before a public announcement was made that the scheme was to close in February 2016.
Asked whether he thought the DUP spads were behind the leaks, Mr Mills replied: "I don't have positive evidence of that, but I couldn't see how else the information was getting out."
Outlining the wrangling between civil servants and the DUP over the winding down of the scheme, Mr Mills also said that the Deti minister, Jonathan Bell, was sidelined with the decision put in the "hands of DUP party officers".
He referred to the statement by the minister in early February 2016 that the RHI initiative was to shut as its costs spiralled.
Within days, Mr Bell suddenly announced that the scheme would remain open for a further fortnight beyond its original closure date.
Mr Mills said that an email from Timothy Cairns explained that, although Mr Bell had approved the closure, "the matter was in the hands of party officers now".
The senior official said he believed it was done "to allow people to make applications before closure".
The inquiry chair, Sir Patrick Coghlin, noted: "It seems that a submission, to be taken by a minister of the executive, was to be dealt with by party officers, according to Mr Cairns. That is a fairly serious matter."
The scheme paid out more in subsidies than the cost of fuel due to a lack of cost controls, causing a potential overspend of £700m over 20 years.
Mr Mills accused DUP advisers of "stalling tactics" regarding changes to the scheme throughout 2015 and said that it was "commonly thought" that Andrew Crawford was "the person pulling the strings".
Mr Crawford was spad to Arlene Foster when she was Deti minister and accompanied her when she became finance minister in May 2015.
Mr Mills said that Dr Crawford's influence - despite no longer working in the department - was "very great still in terms of decisions in Deti".
Mr Mills said he "didn't dissent" from an account that the minister, Jonathan Bell, was "nodding along" during one key meeting as his spad Timothy Cairns made suggestions about delaying the RHI scheme.
However, he added that Dr Crawford exerted the greatest role, with the minister and Mr Cairns "more or less having to go with" his proposals.
Mr Mills was also questioned about whether he was being "redirected back to the spad" when he went to raise issues with the minister.
Sir Patrick Coghlin asked whether in summary "you went to the spad, who is not directly elected, who then goes to the minister..this is the way the politics worked in the department."
Mr Mills replied: "That was the system, as I understand it".
The hearing will sit again today, when it will hear evidence from Tom Forgrave, a poultry farmer and chair of the Ulster Farmers' Union's poultry committee.
He is a key figure in the Renewable Heat Association NI (RHANI), which went to court to stop claimants being identified.
In May 2017 it emerged that Mr Forgrave had received almost £750,000 since the scheme opened.
