Less than a year after being defeated by strong public opposition, the mining industry is planning another bid to gain access to minerals lying beneath the conservation estate, leading industry figures have indicated.

Labour MP David Parker yesterday said "senior" mining industry sources had told him they planned to seek an increase in the size of pockets of Schedule Four land, which may be used for mining related activities.

Under current law, miners could obtain permits to allow "interference" on Schedule Four land restricted to areas 10m by 10m.

That was to allow mining vents or tracks to emergency exits, said Mr Parker.

"It's not intended to facilitate mining in Schedule Four land. That's why what the industry would like to do is have that changed to 30m by 30m which would then allow them to have drilling rigs for prospecting purposes."

Mr Parker understood the industry's objective was "to prove whether there's a valuable resource there, and then you would cause a large amount of pressure to remove an area from Schedule Four protection".

Less than a year ago, public opinion - including a march down Queen St by 20,000 to 40,000 people led by actors Robyn Malcolm and Lucy Lawless - forced the Government into an embarrassing u-turn over its plans to remove Schedule Four protection from 7058ha of the Department of Conservation estate.

That included conservation land in Coromandel, Great Barrier Island and Paparoa National Park North Westland.

Appearing before Parliament's commerce committee yesterday, acting Energy and Resources Minister Hekia Parata and her officials told Mr Parker they were not aware of any approach from the industry to change the Schedule Four regime.

Later, she told the Herald she would not be receptive to any such request.

"Last year, we consulted with New Zealanders on mining and Schedule Four and the answer was resoundingly clear - New Zealanders do not want mining on Schedule Four lands and the outcomes of that review will be incorporated into the Crown Minerals regime."

Chief executive of the Minerals Industry Association Doug Gordon said he was not aware of any specific approach by the industry over the issue but he would support such a move.

He said the intent of legislation and regulations allowing an area 10m by 10m to be cleared of vegetation for low-impact activity was always intended to allow for exploration. However, that area was too small for that, while 400 square metres (10m x 20m) would allow comfortable operation of a drilling rig.

"If you were to prove something up and want to mine there, for example Pike River was on Schedule four, you've got access to the ore body from outside."

Green Party mining spokeswoman Catherine Delahunty said that her party "would be very opposed to any weakening of Schedule Four". "The mining industry are determined to mine within Schedule Four, whether it's going underneath with underground mining or by pushing the rules ... it's basically mining by hook or by crook."

* Was added to the Crown Minerals Act in 1997 and restricts mineral-related activity in specified conservation areas.
* Schedule Four land areas total about 40 per cent of public conservation land including national parks or 13 per cent of New Zealand's total land area.

* Only "minimum impact" activities are permissible in Schedule Four, including geological, geochemical and geophysical surveying, taking samples by hand-held methods, and aerial and land surveying.

* An area of vegetation 10m by 10m or 100sq m might be cleared to allow for such activity.

* Labour says miners are seeking to have that increased to 30m by 30m or 900sq m.