The National Party says the Government's climate change policies are costing taxpayers more than $600 million - a figure Climate Change Issues Minister David Parker disputes.
National environment spokesman Nick Smith said details in a Cabinet paper released to the Herald showed latest indications were that forest owners intend todeforest about 47,000ha during the first Kyoto commitment period between 2008 and 2012.
If that happened, it would add around 32 million tonnes of carbon dioxide equivalent to New Zealand's deficit - worth about $300 million and in effect nearly doubling the deficit.
Under Kyoto's rules, a country earns credits when land is switched from a low-carbon use such as grass to a high-carbon one such as forestry.
When a forest is felled and not replanted, the country is liable for the emission of that stored carbon.
Dr Smith said Labour ratified Kyoto saying New Zealand would have hundreds of millions of credits.
"Last year they admitted they had erred and that we actually had a deficit of 36 million tonnes of carbon.
"In August they said this was a conservative estimate and the situation was expected to improve but official papers now show the deficit will increase by a further 32 million tonnes due to forest clearing."
He accused Labour of bungling.
A spokesman for Mr Parker said the deficit was unchanged, adding the Government was protected from increased liability because it set a cap on how much deforestation was permitted. He said the Cabinet paper was projecting what would happen if there were no cap, as deforestation was expected to happen faster than previously expected.
However, "the cap is there".
Forestry policy was part of the review of climate change policy being undertaken but lifting the cap was not under consideration.
Mr Parker said the Government had made it a priority to look at ways to deal with deforestation "and it is clear we have a number of options available to us that will reduce deforestation rates and address the issue".
"Jim Anderton and I are listening to the forestry industry and working with them.
"Options include encouraging new tree planting of commercial forestry, slowing deforestation and incentivising permanent non-harvest forestry."
How that would be done would go to Cabinet in early April.
