An embarrassing backdown over mining has exposed deep divisions in the Cabinet over the pace of economic reform.

In a major U-turn forced by Prime Minister John Key, the Government has abandoned plans to open up to 7000 hectares of protected conservation land to mining, despite touting it as a key plank of its promised "economic step-change".

Energy and Resources Minister Gerry Brownlee – who was a strong advocate of the policy – will front the announcement today, after National MPs are briefed at their weekly caucus meeting.

It will include a promise not to allow mining on land in the Coromandel, Great Barrier Island and Paparoa National Park, on the West Coast, earmarked as containing mineral resources after a stocktake that identified $140 billion of mineral resources, 70 per cent of which was on the conservation estate.

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