The miners' union has highlighted shortcomings in changes to safety standards recommended by the Department of Labour.
Royal Commission hearings into the Pike River Coal mine disaster are in their final phase. They are looking at policies in place at the time and how these might be changed to prevent future incidents.
Twenty-nine men died at the West Coast mine following a series of explosions that began on 19 November 2010.
On Monday, the department used the Royal Commission to recommend greater worker involvement in maintaining safety in mines.
The Engineering, Printing and Manufacturing Union says that falls well short of the worker-appointed check inspectors used in Australia.
EPMU lawyer Nigel Hampton, QC, told the inquiry on Tuesday the union and the Labour Department's own advice recommended the re-introduction of check inspectors in 2002 and again in 2008.
Mr Hampton then turned to address families of the Pike River miners sitting at the back and said if the department had taken its own advice, the disaster may have been avoided.
Nigel Hampton said through its lack of action, the Department of Labour has forfeited its right to oversee health and safety and this job should now be handed to another agency.
CTU wants corporate manslaughter charge introduced
Earlier, the Council of Trade Unions asked the Royal Commission to recommend the introduction of a criminal offence of corporate manslaughter.
In making its case, the CTU quoted a law paper which said penalties under the Health and Safety Act fail to reflect the moral outrage the community feels when deaths occur in the workplace.
Unlike individual criminal acts, corporate manslaughter holds the individual company liable.
CTU lawyer Ross Wilson told the hearing that Government plans to combine the Department of Labour with three other departments as part of a super business ministry is abhorrent.
Mr Wilson said it would be impossible for such a ministry to have a focus on business, as well as health and safety.
Mr Wilson said the CTU would prefer that a separate Crown agency be set up with the sole purpose of monitoring safety at mines and other workplaces.
The union says this should have similar powers to the Civil Aviation Authority or the Transport Accident Investigation Commission.
Ross Wilson told Radio New Zealand's Checkpoint programme on Tuesday the charge of corporate manslaughter has been introduced in the United Kingdom, Canada and Australia and holds organisations to account for negligence.
Mr Wilson says the penalties range from an unlimited fine to making a company advertise what they have done.