A group of councillors want a dossier on why the Corby Cube ran at least £10m over budget to be made public.
However, the ruling Labour group says the report will not be made fully public because of legal concerns.
The report, which runs into hundreds of pages, was commissioned by Corby Council after Conservative councillors expressed concerns about The Cube, including its cost.
A cross-party sub-committee of the overview and scrutiny panel was convened and members have spent months interviewing people about the multi-million pound project.
Their report was made available to all borough councillors yesterday and the Conservative group immediately called for it to be made public.
A statement from leader of the Conservative group David Sims, and councillors Rob McKellar, Stan Heggs and Ray Lilley, to council leader Tom Beattie, said: “As the official opposition on Corby Borough Council, tasked with holding the administration to account and ensuring that the best interests of the public are served, the Conservative group demand that you release a full and unedited copy of the Corby Cube Scrutiny Report to the general public and to the relevant authorities.
“People in the borough of Corby have a right to know how their taxes are spent and how their council is operating.
“There has been an overspend of £10 million on the Corby Cube project and we consider it to be totally unacceptable for the Labour administration to be hiding the details and reasons behind the overspend from the public.
“This is yet another cover-up from Corby Borough Council and is frankly an affront to transparency and open government.”
Corby Council leader Tom Beattie, said the full council will now have to consider the report along with any recommendations the review group has made and what action the council needs to take now.
He said: “The report contains commercially, financially and legally sensitive information and as such it would be irresponsible for the report to be issued in full as this decision could have detrimental implications to both the council and the taxpayers of Corby.
“Although the full report will not be issued, the review group has decided to issue a summary report to the press and public once councillors have had the opportunity to discuss the outcomes.”
Cllr Beattie said the review group took legal advice and was told that its findings should not be made available to members of the public.
The experts said the decision was justified on the grounds that information was given on a confidential basis by those interviewed about The Cube.
They say that without a confidentiality agreement, full and frank views may not have been given to the panel.
The review group was also advised that making the full report public could prejudice the outcome of potential litigation or adjudications related to disputes between the council, its building contractors and the professional team.
The council is paying £178,000 interest on the overspend on the Cube, which opened in November 2010.
A year ago the council revealed that the cost of the Cube had hit £41.6m, about £5m over budget, but in June that figure was revised and the council said there would need to be further borrowing of £5.5m to fund the building, bringing the total overspend to £10.5m.
The planned rooftop garden and the bistro at The Cube have never opened.