The Stormont special adviser at the centre of the row is Stephen Brimstone, who was accused of putting pressure on a party colleague over another matter.
Lisburn DUP councillor Jenny Palmer, a member of the Housing Executive board, told BBC Spotlight that he tried to pressure her into changing her vote at the board to extend the contract of controversial maintenance firm Red Sky. He was said to have told her "The party comes first – you do what you're told, otherwise there is no point in (you) being on the board..."
Mr Brimstone challenged her version of events, but last summer he and Mrs Palmer met party leader Peter Robinson and afterwards she was shown a statement in which Mr Brimstone "apologised" to her.
She had expected it to be issued publicly and agreed to remain a party member.
But the apology was never made public and there has been no further comment from Mr Brimstone.
Yesterday's report said: "Most members of the committee were unconvinced by Mr Brimstone's evidence that he had not seen a copy of the letter of 2 February 2012 from Turkington Holdings Ltd until July 2013."
The committee also concluded a "lack of challenge" by officials extended to changes to Assembly questions requested by Mr Brimstone.
"Most members found it difficult to believe that senior civil servants accepted the view of the Spad and the minister in relation to the meeting of the 16 April 2012, and allowed this to become the prevailing position of the department, in the face of the facts held by senior officials."
Both the DSD and the DUP last night said Mr Brimstone had nothing to add.