Treasury issued a stern warning to the Government over the huge costs it would face in bringing about substantial cuts to greenhouse gas emissions by 2020, it has emerged.
Treasury documents have been released indicating the Government's goal would be eight times more expensive for New Zealand than for other developed countries.
It says overall emissions have been boosted by a fast-growing population, and much of New Zealand's emissions comes from hard-to-fix agricultural sources.
Treasury recommended emissions should be able to rise by 15% from 1990 levels to keep the cost to New Zealand at a similar level to that facing other developed countries.
The warnings led the Government to cut its target range from 12% to 20% to a band of 10% to 20%.