The government department that oversees workplace safety didn't investigate an air force helicopter crash on Anzac Day, 2010, because it misunderstood the law it enforces, a legal review has found.
An inquiry is set to get underway into the failure of the Department of Labour to investigate health and safety issues behind the crash that killed three Royal New Zealand Air Force servicemen.
However, the inquiry won't look into any actual health and safety failures, because the time limit for prosecution for breaches has passed.
Defence Minister Jonathan Coleman has already ordered a review of safety improvements following the crash.
However, as State Services Minister, Dr Coleman will announce the inquiry into the Department of Labour's incorrect rejection of its responsibility to investigate the crash this week.
The New Zealand Herald reports that the mistake happened because the Department of Labour, which is now part of the Ministry of Business, Innovation and Enterprise (MBIE), believed its responsibility to investigate workplace accidents didn't extend to those involving aircraft.
It referred the matter to the Civil Aviation Authority (CAA), however, the CAA said it had no jurisdiction over military accidents and no investigation was undertaken.
An official in Dr Coleman's office said State Services Commissioner Iain Rennie is establishing an inquiry to find out how the mistake had happened.
MBIE health and safety head Brett Murray said Crown Law has determined that the Department of Labour did have jurisdiction to investigate.
In future military aviation accidents, "the ministry would lead the investigation with support from the CAA", he said.
The issue emerged after the family of one of the men killed questioned the lack of health and safety inquiry, Mr Murray said.