Former Social Development Minister Nelson McCausland acted inappropriately by attempting to extend a Housing Executive contract with a maintenance firm, a Stormont committee has found.
In a report seen by the BBC, it says the move over the Red Sky company was "politically motivated". The DUP has described the report as a "witch-hunt".
The Social Development Committee began an inquiry after a BBC Spotlight programme into alleged political interference in the running of the Housing Executive almost two years ago.
An earlier report on phase one of the inquiry found that Mr McCausland had misled the committee over a meeting he held with an organisation called the Glass and Glazing Federation.
However, the conclusions of the inquiry's final phase three, will make difficult reading for the former minister.
On the "key issue" of whether he acted "inappropriately", the committee concludes that based on the evidence, he did.
The report says it was clear he sought to have the date for a termination notice for the Red Sky contracts extended despite being aware of the adverse findings of the executive itself and independent reports into the company's performance.
And, it says, the decision to seek an extension to the Red Sky contract was "politically motivated".
It goes on: "It is evident to the committee that regardless of a minister's views, or that of his party, these should not be enacted by seeking to change public contracts that are out with the authority of the minister - as the committee believes happened in this case."
The committee also calls for appropriate mechanisms "to ensure that holders of public office can be held accountable".
"While there is currently a mechanism to investigate allegations in relation to the conduct of MLAs and to determine any action to be taken as a result of the findings of an investigation, there is no such equivalent mechanism for investigating allegations of misconduct against ministers," the report adds.
The committee says the questions posed in the Spotlight programme of both Mr McCausland and his special adviser Stephen Brimstone had the potential to undermine public confidence in the political institutions if left unanswered.
It also says the lack of an investigative process, independent of the political institutions, is a "glaring gap" in the assembly's ability to ensure ministerial accountability in the face of charges of misconduct.
The report is being sent to MLAs next week and will be debated in the assembly on 12 May.
The DUP's Sammy Wilson criticised the report: "The very fact that some committee members have sought to publish this report during an election is further evidence to it being a politically motivated witch-hunt from beginning to end.
"The minister was perfectly in his rights to have meetings with public representatives and he did not interfere in any process. This is supported by officials' evidence.
"Nelson identified the NIHE system for maintenance payments was shambolic and therefore reasonably asked that no reallocation of Red Sky's work be made until arrangements were put in place to ensure that no firms guilty of the same practices were rewarded with new contracts."