Environment Minister Nick Smith has defended the Government's national policy statement on freshwater management.
An independent report into the policy commissioned by Fish Game New Zealand says waterways will continue to decline under the policy.
But Dr Smith says the Government has increased its spending fivefold on cleaning up waterways
He told Morning Report that the policy is a step forward and defended the time line.
Water quality policy questioned
The report by the Cawthron Institute says that under the current policy, the state of lakes, rivers and wetlands is likely to decline for several more years.
It says that could be avoided if regional councils limit pollution from intensive land use.
However, the report says Government policy gives councils until 2030 to introduce any changes.
The report says the Government ignored several recommendations from an earlier board of inquiry when it issued a national policy statement on freshwater management in May.