It's prompted by an OECD report which says member countries, including New Zealand, have made little overall progress in reducing water contamination from farming over the past decade.
The report says the rise in commodity prices over recent years has encouraged more intensive production and increased the risk of water pollution.
Green Party water spokesperson, Eugenie Sage, says the OECD report raises concerns about the quality of New Zealand's lowland rivers and streams.
She says the Government is spending millions of dollars of public money on trying to clean up waterways, but failing to control the source of the problem - more intensive farming.
"By subsidising irrigation schemes you will get more intensification, when we've already got severe problems with load in streams and a lot of our lakes."
Eugenie Sage says Government water clean-up grants risk being wasted if cow numbers in sensitive catchments are not controlled.