Making New Zealand's freshwater of a swimmable standard within a generation is the goal the Government's proposed national policy statement on freshwater management, released on Wednesday.
Environment Minister Trevor Mallard says the statement is intended to guide and direct councils to manage waterways better.
Mr Mallard says not all waterways will be swimmable by 2035, and the clean-up will require changes in behaviour.
He says a board of inquiry has been set up to lead public consultation on the standard.
But the National Party says the statement is too little too late.
Environment spokesperson Nick Smith says the Government has overseen almost nine years of significant deterioration in New Zealand's water quality.
He says the statement will take many years to have any impact on water quality.