Jonathan Bell claims he was told he would not be able to challenge the botched Renewable Heat Incentive (RHI) scheme because two DUP special advisers "have extensive interests in the poultry industry".
Mr Bell made the allegation on Monday evening while speaking under parliamentary privilege in the Northern Ireland Assembly.
The advisers named by Mr Bell, Timothy Johnston and John Robinson, have denied the allegations.
The DUP said in a statement: "Following unsubstantiated allegations made by Jonathan Bell in the Assembly chamber under the cover of Privilege we wish to point out that:
"Timothy Johnston has no interests whatsoever in the poultry industry and does not benefit or have any family members who applied to or benefit from RHI
"John Robinson has no personal interest in the poultry industry. His family home farm have chicken houses but are not part of the RHI scheme and never have been recipients or applicants.
"These are outrageous, untrue and unfounded allegations are nothing short of mud-slinging."