The Government will today scrap hugely controversial plans to mine some of the country's most pristine conservation land.

The Herald understands the Key Administration will rule out mining in all 7068ha of conservation land it was considering opening to prospecting, including parts of Great Barrier Island, the Coromandel Peninsula and Paparoa National Park on the West Coast.

It is an acutely embarrassing u-turn for National, which faced furious public opposition to the plans.

Energy and Resources Minister Gerry Brownlee, who strongly pushed for mining firms to be allowed into what are no-go areas for mineral exploitation, will carry the can for a policy defeat brought about by the uproar.

He is also expected to announce that not only will there be no mining in those areas, all national parks will be protected in future.

Mr Brownlee may be able to save some face by flagging more mining on Crown land of lower ecological value.

He may also try to divert attention from his backdown by signalling increased Government efforts to develop New Zealand's oil, gas and mineral potential, including offshore.

Yesterday, Prime Minister John Key spoke of mining still being capable of delivering economic benefits - suggesting the announcement will be wider than just a backdown on Schedule Four, a protection for high-value conservation land introduced by National in the 1990s.

"Schedule Four is one part of the equation and we'll be having that discussion tomorrow, but in terms of the wider mineral and exploration opportunities in New Zealand, it's my opinion they can deliver a step change."

Mr Key pointed to the opportunities outside conservation areas, including lignite and iron sands. "They are not insubstantial by any stretch of the imagination."

Mining opponents last night welcomed the imminent backdown.

Environmental Defence Society chairman Gary Taylor said mining would have clashed with NZ's "clean, green brand and image".

Mining on some of the "precious bits" of the country was not the way to go, he said, given there were so many other suitable areas.

Coromandel Watchdog spokesman Denis Tegg said his organisation had "champagne on ice and are ready to celebrate as soon as the decision is officially confirmed".

It was happy the Government had backed off Mr Brownlee's "stupid and over-hyped" plan for the Coromandel Peninsula.

Official documents show that last year, Government officials suggested removing protection from all high-value conservation land to give mining companies easier access to it.

Subsequent Cabinet papers show Mr Brownlee and Conservation Minister Kate Wilkinson recommended the removal of Schedule Four protection from 467,517ha, including more than a third of Kahurangi National Park west of Nelson and most of the 73,820ha protected in the Coromandel.

The "stocktake" announced in March saw that whittled down to 7058ha, including parts of Great Barrier, Coromandel and Paparoa.

A consultation document on the plan drew more than 30,000 submissions, nearly 50,000 people signed a Greens-organised petition against it and 15,000 marched in Auckland.

High-profile New Zealanders, including actresses Lucy Lawless and Robyn Malcolm, have also been vocal in opposing the plans.

In a sign the Government has taken note of the outcry, it is also understood to be considering legislative changes to extend Schedule Four protection to all national parks.

Aside from the Schedule Four areas earmarked earlier this year for prospecting, Mr Brownlee also said about $4 million was to be spent gathering information about further conservation estate areas, including some protected under Schedule Four.

They included Northland, the Kaikoura Ranges, Dun Mountain east of Nelson, the Longwood area in Southland and parts of Stewart Island.

$4.3 billion - estimated value of gold and silver on Great Barrier Island.

$54 billion - estimated value of mainly gold and silver on Coromandel Peninsula.

- additional reporting by Vaimoana Tapaleao, NZPA