Queensland will end its experiment with privately run jails after a scathing report found it was hard to know what was really going on inside them.

The government will retake control of the state’s two privately run prisons, costing taxpayers an extra $111m over four years.

The Arthur Gorrie Correctional Centre and Southern Queensland Correctional Centre will get more staff when they return to public operation once the existing contracts expire.

The government cited concerns about the number of staff assaults at the privately run jails.

But that was just one of the concerns detailed in a Crime and Corruption Commission report on Queensland’s prison system, released last year.

The report said the two prisons were run by multinational, profit-driven corporations that had their own ethical climate and “tone at the top”.

“This marketised approach, where prisons are operated by private, profit-driven organisations, disconnects the state from direct responsibility for the delivery of privately operated prisons,” the report said.

“This model creates challenges for the state in ensuring prisoners detained in privately operated facilities are treated humanely and have appropriate access to programs and services.”

The same report found the entire prison system was overcrowded. It cited alleged instances of staff supplying drugs or weapons to inmates, colluding to avoid searches and allegedly coaxing prisoners to bash fellow inmates.

On Tuesday, the corrective services minister, Mark Ryan, said ending the private jails experiment would “strengthen corruption resistance in Queensland prisons”.

“This will lead to greater safety” he said.

Staff at the two prisons will be given priority to take up positions once they return to public operation.