The government can already rely on a bare majority to push through changes environmental legislation, as battle lines are drawn ahead of a speech by Environment Minister Dr Nick Smith.

In an annual speech to the Nelson Rotary Club on Wednesday, Smith will outline the likely changes National will propose to the Resource Management Act.

During the last term electoral term National proposed changes to the section of the act relating to the principles of the legislation, which critics claimed favoured economic development.

It failed to bring it before the House, after both United Future and the Maori Party warned they would not support it.

Even before Smith has announced his plans, which are expected to show both the government's approach and the timing, two of National's government partners have already indicated a similar stance to last year.

David Seymour, the MP for Epsom and the ACT Party's sole Member of Parliament said reform of the RMA was "extremely urgent" if cities were to be allowed to grow and more affordable housing made available.

"There's a strong anti-development bias running through it [the RMA] and of course councils are required to follow the RMA when making their plans and giving consents, so that flows through to a bias against cities growing and providing the supply of housing that younger New Zealanders need to come on stream."

National's 60 MPs means that with the support of Seymour it has the smallest possible majority needed to pass legislation.

United Future's leader Peter Dunne, the MP for Ohariu, said pushing through changes with a bare majority on such a key piece of legislation would sent the wrong signal.

Dunne has signalled that he will not support changes to the legislation which he says could undermine the environmental elements of the legislation. To do so would turn the legislation "developers' charter" Dunne warned today.



"By tampering with the principles you simply relegate the act and environmental concerns to simply being another part of the process, not the bedrock on which development should occur," Dunne said.

Yesterday Smith gave little detail about whether he planned to propose changes to the principals sections of the act, but signalled a plan to improve the process for residential construction.

"There is no question that the Resource Management Act is not working in delivering New Zealanders affordable housing, particularly in places like Auckland," Smith said on Monday.

Labour has maintained a wait and see approach ahead of seeing the government's plans.

Leader Andrew Little said there were problems with the current RMA in terms of its impact on housing affordability, but the party did not want to see environmental protections weakened, or undermine the input of local communities.