The Parliamentary Commissioner for the Environment makes a "circular argument" about mining and the previous government was led by a "bunch of muppets", Prime Minister John Key said today.
The Government last month released a discussion document proposing removing some conservation areas from Schedule 4 of the Crown Minerals Act, which protects them from mining.
Those areas include parts of Great Barrier Island, the Coromandel and Paparoa National Park.
Parliamentary Commissioner for the Environment Jan Wright said yesterday the Government had not made a case for opening up certain land to mining.
There was a lack of information available about the conservation value of the land, the benefit of mining it and problems raised by the joint access approval, she said.
Labour leader Phil Goff said the public knew that "long before they were brought into this discussion National had made a secret deal with the mining interests to mine protected areas, even before the election".
Mr Key said in Parliament today he could "only assume the leader of the Opposition is desperate to get on TV if he wants to make things up".
"The difference between this Government and the previous administration is we take things to Cabinet and have genuine conversation. Under the previous government they were all a bunch of muppets that just agreed with what the prime minister thought."
Mr Key said today Dr Wright had made a circular argument -- "we should only remove land (from Schedule 4) where the mineral value outweighs the conservation values. Actually we can't determine that unless we do remove things".
He said the Government had been conservative with the 8200 hectares of land it proposed to open up for mining when officials had suggested 467,000ha.
Energy and Resources Minister Gerry Brownlee said yesterday the only way the Government could find out whether the land had significant mineral value was by removing the Schedule 4 ban on exploration.
"You can go out there with a pick and shovel but you need to go and explore the thing before you know exactly what's there."