Mr Hoggard said he isn't sure if the Greens have thought of all the policy's potential consequences.
"It'll affect a lot of people - I guess the big question is what are you trying to do with such a proposal: Is it revenue gathering? Is it about discouraging use of water?"
Mr Shaw also announced a plan to crack down on water bottling companies and exporters, promising put an immediate 10 cents a litre levy on sales or exports of bottled still and sparkling water.
He said putting a price on water, solidifies its value to New Zealand - even if it only makes us about $3 million per year.
Mr Shaw said this is what the public want, and while it's not a lot of cash, it sends a signal.
"A lot of bottling companies know that this is coming - that you cannot simply take a resource for free and then make a profit out of it."
The Greens came out of their Nelson campaign launch all guns blazing, saying they must be stronger than NZ First in a left-wing Government.
The two parties poll consistently around 10 per cent, and it's likely both will be required if there's a change of Government in September.
But in the past 24 hours Green co-leader Metiria Turei has called New Zealand First's immigration policy racist, and Winston Peters has warned them of name-calling, saying there could be consequences.
Ms Turei didn't rule out working with them, but said it's not her preference.
"I don't like that NZ First engages in this racist divisive politics - I don't like it at all.
"I'm asking New Zealanders to strengthen our arm in the next government so they don't have that kind of influence in a truly progressive government."
