The Government has rejected calls to reinstate a system of on-site mine safety inspectors.
The Engineering, Printing and Manufacturing Union wants the system, which was abolished in the early 1990s, brought back.
The union says the system is a vital protection for workers.
The union's head, Andrew Little, said a Department of Labour review in 2008 found that New Zealand's mining standards lagged behind those in many Australian states.
Mr Little believed the report was overlooked and urged the Government to look at the report's recommendations after the Pike River Coal disaster was dealt with.
In a submission to the review in 2008, Pike River Coal also asked that more mine inspectors be made available.
But Labour Minister Kate Wilkinson says the Department of Labour has advised her there were often unproductive stand-offs between the inspectors and mine managers, and the system should not be brought back.
Ms Wilkinson says Cabinet has already been debating changes requiring a higher level of competency for mine managers with fewer than 20 workers.
International mine safety adviser David Feickert says the old system formed a safety triangle involving the mine manager, a powerful government mine inspector and an independent on-site inspector.
Mr Feickert says the system is still in place in Australia and Britain, and those countries have a lower level of incidents.
He says the inquiry after the Pike River Coal mine disaster must include international experts who can compare New Zealand's safety structure with other models.