WorkSafe completed 417 investigations in response to serious health and safety breaches in the year to 30 June 2017, the agency says in its annual report.

It initiated 73 prosecutions and completed 66 of these, with 88% being successful.

WorkSafe says the success rate reflects the high quality of its investigation and legal processes.

"Enforcement forms part of a well-functioning regulatory system (providing both deterrence and accountability). WorkSafe uses its suite of enforcement tools (from notices through to prosecutions) to encourage changes in behaviours and practices across the health and safety system. Being credible, fair and proportionate are fundamental principles that inform our enforcement approach," the report says.

"We take an open and transparent approach to how we use our enforcement tools so duty-holders clearly understand what is required of them. Our publicly available Enforcement Policy and Enforcement Decision Making Model set clear guidance so that duty-holders know when and how we will use our enforcement tools."

The report says there was wide interest in WorkSafe's use of the enforceable undertaking tool provided under the new regulatory regime.

"EUs now form part of WorkSafe's wider suite of enforcement tools, providing an alternative means to prosecution to hold duty-holders to account while delivering benefits to workers, industry and the community. WorkSafe accepted two Enforceable Undertakings in 2016/17."