The Parliamentary Commissioner for the Environment is calling for law changes to better protect New Zealand's rivers from development.
A report released by Jan Wright says there are gaps in the current legislation that companies wanting to install hydro-electric schemes can take advantage of.
Dr Wright is concerned at how little protection there is for rivers, particularly in the North Island where few have any protection at all, and recommends that greater powers be given to the Department of Conservation.
The commissioner also wants changes to the Resource Management Act to remove what she says is a bias towards hydro-electricity.
She believes hydro-electricity is better for the environment than power stations, which burn coal and gas.
However, Dr Wright says these schemes can destroy rivers, which are vital to New Zealand's image.