TORONTO - New details about the extent of a corruption probe into three Ontario government ministries prompted the opposition Wednesday to demand the resignations of three cabinet ministers.

The OPP's anti-rackets division raided the ministries of Transportation, Economic Development and Trade, and Community and Social Services on July 15 as part of a probe into "irregular financial transactions" with outside vendors.

The search warrants remain sealed, but there were allegations government employees accepted cash and other kickbacks in exchange for inflating the value of government maintenance contracts and for telling one vendor the level of any competing bids.

In a one-page overview filed with the court, provincial police said the investigation involved "various criminal offences" by Ontario civil servants in the three ministries, as well as outside contractors who cleaned carpets in government buildings.

The total amount of the fraud uncovered so far is about $400,000, the police document alleged.

"Employees of two facility management companies, SNC Lavalin Profac and CB Richard Ellis, are also believed to have been involved in the alleged criminal offences, along with a vendor of record who provided services to government," stated the police overview.

The OPP has not laid any charges in connection with the raid on the government offices, Insp. Dave Ross said Wednesday, and the investigation continues.

Instead of trying to distance themselves from the scandal, it's time Liberal cabinet ministers accepted responsibility for not catching the fraud themselves, said NDP justice critic Peter Kormos.

"I think there (are) ministers that have to resign," said Kormos.

"It's important that ministers be responsible for what happens in his or her ministry. We have not seen that ministerial responsibility or accountability and I find that very, very shameful."

The ministers -- Kathleen Wynne, Sandra Pupatello, and Madeleine Meilleur -- should step aside at least until the investigation and any prosecutions are completed, added Kormos.

"It's pretty obvious that there's fraud and corruption taking place in some of these ministries, and at the end of the day we shouldn't need the OPP to be investigating this," he said.

"We should be able to rely on the political oversight of a ministry and that clearly has been sorely lacking."

The Progressive Conservatives noted that the public still doesn't know the whole story behind the corruption probe, but said if the allegations are true then the ministers must resign.

"There are serious allegations which if proven to be true means these ministers didn't do their jobs, put the public service in Ontario at risk and put tax dollars in harm's way," said Opposition critic Lisa MacLeod.

"If this is true, these three ministers must be held responsible, but they'd better start coming clean today."

The police overview alleged government workers and employees of SNC Lavalin and CB Richard Ellis, companies that managed the cleaning contracts for the provincial buildings, were involved in the scheme.

"The employees who were involved in the awarding of service work, typically carpet cleaning, to a VOR (vendor of record), would accept kickbacks from the VOR in the form of cash payments, the provision of free personal services and or the provision of personal electronics," the police statement alleges.

"In some instances the invoices were false in that no work was actually done. In other instances the dollar value of the invoices was inflated ... (and) the VOR provided the suspect employee with approximately 50 per cent of the inflated amount."