Treasury says the risks surrounding the Government's new emissions trading scheme have been poorly assessed.

The Climate Change Response (Moderated Emissions Trading) Amendment Bill was introduced to Parliament under urgency yesterday and got through its first reading with the support of the Maori Party.

The scheme seeks to limit emissions, which New Zealand is required to do under international agreements.

The Labour government passed an emissions scheme just before last year's election but National pledged a redesign as it considered Labour's scheme would be too costly for the economy.

Now Treasury officials say the quality of analysis of the new bill's impact was "not commensurate with the significance of the proposals".

There was no clear analytical basis for the proposal to align some key design elements with Australia's scheme.

They highlighted the dangers of aligning with Australia before Canberra's scheme had even been finalised. Almost half of New Zealand's greenhouse gas emissions come from agriculture, compared with Australia's heavy reliance on coal-fired power stations.

"Such risks may include the potential impacts on business certainty and investment decisions, and the overall credibility, sustainability and effectiveness of the New Zealand ETS."

The unusually strong criticisms are included in a preamble to the bill.

National won the backing of the Maori Party for the bill to proceed to a select committee, but talks with Labour on a possible bipartisan deal have collapsed.

The draft bill shows the changes will cost taxpayers $415 million by 2013, before moving into the black over the next four years. However, as the price of longer-term assistance to big polluters takes effect, the bill for taxpayers blows out to $2 billion by 2030.

Labour's climate change spokesman, Charles Chauvel, said National was playing a high-stakes game. "Its scheme will cost taxpayers an additional $2 billion up to 2030 and half a billion dollars each year thereafter."