The Labour Party says it expects the Government to back off the prospect of mining on Great Barrier Island and in Coromandel in the wake of one of the biggest protest marches in New Zealand's recent history.

Former prime minister Mike Moore has also weighed in, saying he expects the Government to just "wet its finger" and work out another plan.

The Government is seeking feedback on removing 7058ha of conservation land, which is currently protected, from Schedule Four of the Crown Minerals Act.

Between 20,000 and 40,000 people - including actors Robyn Malcolm and Lucy Lawless - marched on Saturday against the proposal to open up conservation land to the prospect of mining.

Auckland City Mayor John Banks, who opposes the inclusion of Great Barrier in the Government's plans, said he was impressed as he watched the march from the Town Hall.

"They were very noisy and certainly made their point. I've never seen a march as big as that on Queen St. I was impressed. You had to be."

Energy Minister Gerry Brownlee said his assessment of public opinion was that it was evenly divided.

"The Government noticed the march; it would be impossible not to. However, we have a process in place and we will honour that process and won't be making decisions prior to a consideration of all the submissions."

He said that as a New Zealand ambassador, Mr Moore should not be talking about policy matters.

Labour Party leader Phil Goff, who has pledged to return any land removed from Schedule Four, warned the Government that it would ignore public opinion "at its own peril".

A TV3 poll last week showed 52.7 per cent opposed to mining on previously protected land and 39.5 per cent in favour. Two-thirds said they did not want mining on Great Barrier Island.

"They [the Government] have got to back down from both Great Barrier Island and the Coromandel," Mr Goff said.

The Government has said it would go ahead with the mining proposals only if strict conditions were met, including whether it could be done in an environmentally sustainable way.

Last week, the Parliamentary Commissioner for the Environment, Jan Wright, criticised the Government's discussion document - which has drawn 14,000 submissions from the public - as incoherent.

Dr Wright said it did not adequately measure the value of minerals claimed to be in the denoted areas.

The Government has already diluted original proposals, which were revealed in Cabinet papers showing that close to 470,000ha was to be considered for opening up to mining.

The period for public submissions closes on May 26.