The mining industry is questioning a study which found uncontrolled mining could leave New Zealand with a legacy of toxic sites.
The report by the Parliamentary Commissioner for the Environment found 111 mining licences covering 82 mines have few, if any, enforceable environmental controls.
The licences were issued under old legislation, predating the tougher Resource Management Act.
Among the 82 mines is the giant Martha open-cast gold mine in Waihi.
Senior manager Kelvin Eglinton says while the mine might have begun life under old legislation, it later gained approval from the Resource Management Act.
The licence only allows the company to access minerals and it must still go through the consent process under the RMA, he says.
Mr Eglinton says the company has paid a $25 million bond to protect environmental standards which will not be released until the site is rehabilitated.
Neighbouring mine Golden Cross, which has closed down and is being rehabilitated, is still bonded to the tune of $12 million.
In her report, Commissioner Jan Wright Wright cited cases such as a toxic waste site at Mapua near Nelson and the mercury-contiminated Tui mine site in Waikato as examples of risks that could ensue.
She says she came upon the problem while researching Solid Energy's Stockton Mine in Buller, which she praised for its environmental improvements.
But she said mining licences issued before legislation such as the Resource Management Act generally have very few environmental controls.
She said some of these mines might be operating safely, but there are few mechanisms to control them if they are not.