United Future and the Maori Party have teamed up to block the Government's major reforms of the Resource Management Act.
The two parties said this morning they could not support the latest changes to the Act and had written to Environment Minister Amy Adams with their concerns.
Government needed either United Future or the Maori Party's support to get the legislation over the line.
United Future leader Peter Dunne and Maori co-leader Tariana Turia said the amendments to the RMA went much further than rebalancing the legislation to streamline consents.
"We say the changes to remove emphasis on the 'maintenance and enhancement of the quality of the environment' fundamentally rewrite the Act and put a spanner in the works of the legal system, that will take years of litigation to fix up," they said in a joint statement this morning.