The Department of Corrections reports it has an informal understanding with WorkSafe around reporting injuries to prisoners.

It's responding to a 3News story claiming under-fire prison operator Serco is sidestepping health and safety laws by not reporting incidents where people have been seriously harmed.

Corrections has taken legal advice and said it doesn't consider that prisoner-on-prisoner assault or prisoner self-harm should be reported to WorkSafe because they aren't employees.

Spokesman Vincent Arbuckle said only injuries that happen in the course of employment or educational activities are lodged with WorkSafe, and Serco does the same.

He adds assaults are managed internally by Corrections, and referred to police on a case-by-case basis.