Fish and Game says New Zealand's most polluted lake will get even worse if urgent action is not taken to reduce the negative impacts of farming in the area.
In a report released Tuesday the Parliamentary Commissioner for the Environment explained how pathogens, sediment and nutrients are degrading water quality throughout the country.
Fish and Game's environment officer for North Canterbury, Tony Hawker, says Lake Ellesmere will continue to suffer unless drastic measures are taken to combat the effects of a new Canterbury irrigation scheme that is close to being approved.
Mr Hawker says an $11 million clean up plan, pledged last year by the Government and several local bodies, will not make a difference if the irrigation scheme goes ahead.
He says farmers need to start making changes.