Wellington, March 16 NZPA - The Government did not deny in Parliament today that it plans to give the mining industry a $4 million subsidy to survey three national parks.

"I'm not in a position to confirm that at this time," said Prime Minister John Key when he was questioned by Green Party co-leader Metiria Turei.

"What I can say is that when the discussion document is released, New Zealanders will have an opportunity to assess its merits."

Ms Turei wanted confirmation that a $4m subsidy was in the pipeline for the mining industry to survey Kahurangi, Mt Aspiring and Rakiura national parks.

"Does the prime minister believe the New Zealand public would accept his government giving away a $4m subsidy to mining companies to explore mining in the public's national parks," she asked.

Mr Key again referred to the discussion document that is being prepared, which will set out the Government's proposals for mining in conservation land. There is no firm date for its release.

"I think when the discussion document is released New Zealanders will have an opportunity to see how balanced the approach is that the Government is taking," he said.

"That balance is between economic opportunities and environmental responsibilities."

The Government's intentions are being strongly debated by opposition parties.

The Government last year carried out a stocktake of minerals in the conservation estate, which have an estimated value of at least $140 billion.

How much it decides to allow to be mined, and where, is being strongly debated by opposition MPs who believe mining in high quality conservation areas will be unacceptable to the public.

The Labour Party says the discussion document should be released immediately, and party leader Phil Goff also questioned Mr Key in Parliament today.

He didn't get any further than Ms Turei, with Mr Key telling him to wait for the discussion document.

Forest and Bird says the Government is planning to allow mining in 7000 hectares of high value conservation land in the West Coast's Paparoa National Park, Great Barrier Island and the Coromandel Peninsula.

Mr Key has not confirmed or denied that, saying yesterday that leaked information was not necessarily correct.