Arlene Foster has said her party did not try to deflect attention from its alleged involvement in delays in tackling an overspending green energy scheme.
Attention has focused on the role of the DUP’s special advisers to ministers during a period in 2015 when civil servants wanted to curb the spiralling cost of the Renewable Heat Incentive (RHI).
The introduction of cost controls was significantly delayed.
The party’s handling of the botched scheme allegedly led to the collapse of Stormont powersharing.
DUP leader and former Stormont first minister Mrs Foster is due to give evidence on Tuesday to a public inquiry into the affair.
In written evidence she said: “While there was no party narrative, I do believe that there was a prevailing view that Timothy Johnston was not involved in delaying the introduction of cost controls.”
Mr Johnston is chief executive of the DUP and at the time was a special adviser to then first minister Peter Robinson.
Another party special adviser, Andrew Crawford, resigned after a senior civil servant, Andrew McCormick, said he exerted influence over the delays in curbing the scheme.
The scheme was paying too high a level of tariffs for heat generated, leading to allegations it was encouraging businesses to earn “cash for ash” and waste heat to earn subsidies.
Mr McCormick told the inquiry the DUP was concerned to deflect or discredit any possible reference to Mr Johnston, and ultimately acquiesced with the necessity (as it appeared at the time) of naming Dr Crawford as the instigator of the delay.
Dr Crawford had a number of close relatives with boilers registered in the RHI scheme but denied any wrongdoing.
Mrs Foster took issue with some of the written questions she was asked by a solicitor for the public inquiry.
She wrote: “This question and those above at a and b assume that Dr McCormick is correct in his suggestion that there were attempts to deflect or discredit reference to Timothy Johnston. There were no such attempts.
“I recall no such discussions about deflecting or discrediting reference to Timothy Johnston.”
The public inquiry is led by retired judge Sir Patrick Coghlin and is conducting hearings at the Stormont Assembly in Belfast.
The Assembly has not sat for months after the RHI prompted a major falling out between former coalition partners Sinn Fein and the DUP.
Mrs Foster also addressed a meeting she had with former enterprise minister Jonathan Bell about the closure of the scheme, after cost controls had been imposed.
Mr Bell wanted to shut down the scheme as soon as possible in February 2016, when others wanted to allow time for businesses still applying to complete the process.
Mrs Foster wrote: “I recall Timothy Johnston and I trying to explain to him that in light of the public outcry, keeping the scheme open for a further period of time was taking account of the public’s concerns.
“Jonathan Bell was completely opposed to the idea of any additional time from the outset.
“I do not recall him telling me at that time that he would make an announcement to extend by a further period, but he subsequently did announce an additional two weeks so that the scheme would eventually close on 29 February 2016.”