Four repair contractors at the centre of an estimated £18 million overpayment by the Housing Executive have threatened legal action.
They have instructed lawyers and said they were upset and dismayed by allegations made by Housing Minister Nelson McCausland.
The overpaid contractors were Bann Ltd, Dixon's Contractors, Mascott Construction Ltd and PK Murphy Construction Ltd, the minister said.
A statement from the businesses said: "We are particularly offended by the implications of 'wilful corruption' and 'overcharging' on the part of our companies or any of our staff. We shall be mounting a strenuous challenge to this matter, as such outrageous allegations are very damaging to our reputation and our businesses.
"Having sought legal advice we have now instructed solicitors to pursue this matter as vigorously as possible."
Mr McCausland has said the scale of what was uncovered at the Housing Executive was a scandal.
The claims centred on £172 million of work carried out by four firms on around 60,000 homes between January 2008 and the start of this year. Maintenance works included kitchen replacements, double glazing and external improvements.
An external probe was commissioned by the board of the social housing body after an internal review identified major issues over how contracts were handled.
The minister has warned the Executive had already failed to demonstrate the required response to known shortfalls in contract management and said heads would have rolled had £18 million been overpaid by a private company.
The Executive said it has commenced "appropriate action", including legal proceedings, to recover overpayments, adding contractors would not receive any new orders until the issue was resolved.