Changes to the Resource Management Act would have negative effects on the environment, the Green Party said.

A bill to overhaul the Act is back for its second reading this week.

If passed, the bill would allow Environment Minister Nick Smith to override some local council decisions.

Co-leader James Shaw said the tweaks would weaken laws that protect freshwater, public conservation land and the coastal environment.

There would also be less control over urban sprawl.

"When you look at National's track record on the RMA they have consistently undermined it over many, many years."

The bill has the backing of the Maori Party, which would give the Government enough support to pass the changes through Parliament.

Mr Shaw said it would be a gift to property developers at the expense of the environment.

"National has never liked the Resource Management Act and has always wanted to weaken it in favour of economic growth and unconstrained development."