The Green Party says the Government needs to stop issuing mining exploration permits for gold, in order to live up to an international treaty to control mercury.
The Government has signed a United Nations Convention to reduce and ultimately eliminate the use of the toxin mercury and its emissions.
The toxin can cause permanent damage to the nervous system and can also accumulate in the food chain.
Greens' environment spokesperson Catherine Delahunty says gold mining is a big emitter of mercury.
She says the Government is contradicting the treaty by permitting gold exploration on old mercury mines in Northland.
Ms Delahunty says the Government needs to re-think its mining policy, given that coal production can also result in the release of mercury emissions.
Earlier, Environment Minister Amy Adams said the international treaty should not result in any major mining changes in this country.
Ms Adams said the treaty bans mercury mining and places restrictions on some gold and mineral mining. She said mercury mining is not done in New Zealand.
The minister said if the treaty is ratified, the importation of products containing mercury, such as batteries, lamps and thermometers, would have to be phased out.