New Zealand companies are exporting millions of litres of water every year and they're not paying anything for it, the Greens say.
The party is renewing its call for a moratorium on new water bottling projects, saying there are 74 plants already.
"When the water is purely for export it means we're giving it away for nothing," MP Catherine Delahunty told RNZ.
Companies which use the water pay only for consents and compliance costs.
Last Saturday there was a protest march in Ashburton, where the council wants to sell a 10ha site with the right to extract 40 billion litres of water from the local aquifer over the next 30 years.
The buyer is reported to be a company interested in setting up a bottling plant.