The Democratic Unionists stood accused of putting party before the public interest during an angry Stormont debate on a committee inquiry that found one of their former ministers acted inappropriately.
The investigation by the Department of Social Development's scrutiny committee said that ex-DSD minister Nelson McCausland's attempts to extend maintenance firm Red Sky's multimillion-pound contract with the Northern Ireland Housing Executive were "politically motivated".
But the DUP rejected the findings, with Mr McCausland himself branding the inquiry a "witch hunt".
The damning committee conclusions, reached after an 18-month investigation, had already leaked into the public domain ahead of today's fiery exchanges in the chamber - where DUP members and rivals MLAs repeatedly clashed.
Sinn Fein's Mickey Brady insisted the findings were reached after a "painstaking and detailed process of evidence gathering".
"On the key issue of whether the minister acted inappropriately the committee concluded, based on the evidence it received, that he did," he said.
"The committee has also concluded that the minister's actions were politically motivated."
Alliance MLA Stewart Dickson condemned the former minister and his party colleagues.
"This is a story that demands resignations, a story that demands integrity in public office," he said.
"Sadly, the story today will be one of denial and refusal to do the right thing - that will be the order of the day for that party (the DUP). A sad and sorry tale - one I hope the public will judge the players harshly, especially when it comes to elections to this assembly in the future."
Ulster Unionist Roy Beggs said the DUP had "circled the wagons" since the allegations came to light and had attempted to frustrate the DSD probe.
"I suspect that many in the DUP are pleased that this report is only now being aired and the issues were not raised before the General Election," he said.
The SDLP's Dolores Kelly said the DUP had "put the party first" at the expense of the "public interest".
"Their public representatives have put the party first yet again," she said.
Mrs Kelly said the report had exposed "political interference at the highest level".
Traditional Unionist Voice (TUV) leader Jim Allister was scathing in his assessment of the DUP.
"This Red Sky escapade and the political involvement in it has to be one of the worst excesses of abuse of power that has been seen under devolution," he said.
But DUP representatives denounced the committee findings. Party members sitting on the DSD committee produced their own "minority report" that defended Mr McCausland.
The former minister took the opportunity to make his own case in the Assembly.
"It's high on innuendo and supposition, but short on solid argument and evidence," said Mr McCausland.
"Quite frankly it's 1,100 pages long, but not worth the paper it's written on - in fact a waste of good paper.
"The truth is many members of the committee had their minds made up before they started and they weren't going to let the evidence, or lack of evidence, get in the way of a pre-determined outcome."
He added: "I think this report is simply a witch-hunt."
The inquiry focused on Mr McCausland's attempt to get the NI Housing Executive to extend Red Sky's £8 million-a-year contract for maintenance on its social housing stock, despite concerns being raised about the work it carried out.
The Housing Executive is an arm's length body under the DSD, but it retains responsibility for contractual matters.
Red Sky, a company based in east Belfast - a key constituency for the DUP, had been informed by the House Executive in 2011 that its contract was to be terminated.
The firm subsequently went into administration.
The committee questioned the minister's attendance at a meeting with representatives from the defunct Red Sky company, without the administrators present, that discussed the contract situation.
It examined the minister's subsequent attempt to get the Housing Executive to extend the contract.
Such an extension, it was alleged, would have given the former Red Sky directors the opportunity to set up a new firm and bid for the tender.
The investigation also focused on the conduct of Mr McCausland's special adviser Stephen Brimstone - specifically an allegation he tried to pressurise DUP councillor Jenny Palmer, who was a member of the Housing Executive Board, to change her vote at a board meeting considering the Red Sky contract.
The committee noted that a fact-finding investigation by the civil service into this incident recommended that Mr Brimstone face disciplinary action, but that Mr McCausland declined to initiate any.
The committee report said changes were needed at Stormont to establish more robust methods for holding ministers, and their advisers, to account.
All the allegations were brought to public attention by a BBC NI Spotlight documentary aired in July 2013.
The current DSD minister, the DUP's Mervyn Storey, was obliged to formally respond to the report on the Assembly floor.
He described Mr McCausland as a "colleague and friend".
"I concur with what my (DUP) colleagues said in this House today - what we have seen is something that is lacking in substance and surely lacking in any great evidence," he added.
At the close of the debate, a motion noting the DSD committee report findings was carried 55 votes to 32.