The fledgling Environmental Protection Agency (EPA) is being promoted as a possible regulator of regional councils.
Wellington Regional Council has admitted it erred when it told Wainuiomata residents in November that soil from the Waiwhetu Stream, which was dumped in a landfill at Wainuiomata, was safe.
Tests have revealed the soil was heavily contaminated with lead.
Environmental Defence Society chair Gary Taylor says the EPA was set up this year to help speed up big infrastructure projects.
He says its role could be expanded to include the oversight of regional councils.
However, Environment Minister Nick Smith says it will be next year before the Government decides whether the agency will have legal oversight over councils.