National leader Simon Bridges says he is open to the idea of a water tax on bottled water.
"I've always thought that's not a bad idea, but the reality is how you get there is really complex," Mr Bridges told The AM Show on Monday.
"As soon as you put a price on water there will be a variety of interest groups, including iwi, taking you to court."
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Labour's proposed 2c per 1000 litres levy on commercial use was canned when the party did a deal with NZ First to form the Government. NZ First only wanted the levy to apply to bottled water, saying Labour's plan would result in cabbages costing $18 each.
Mr Bridges said water rights was a "hard issue" for National when it was in power.
"We were working our way through it. We understand New Zealanders don't like the fact free water is going offshore and not getting something for that. I'd say every party in Parliament has that view. But is it an easy one to solve? No. Let's see if the Greens' review gets there."
The Greens on Sunday announced a review will look into whether water extraction should be a factor when offshore entities want to buy land.
"If offshore water companies want to come here and buy our land so they can also take our water, we think community issues and concerns should be part of the legal considerations if we're going to grant them those land sale applications," co-leader Marama Davidson told The AM Show.
The review was inspired by the recent sale of of rural land near Whakatane to a Chinese water bottling company, which Land Information Minister Eugenie Sage - a Green MP - said couldn't be stopped under the law.
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Ms Davidson said blocking the sale could have opened up New Zealand to legal action.
Mr Bridges said while National opposes blocking sales to companies who just want to extract our water, he's open to the idea of a levy.
"I think actually if you could get though somewhere somehow to a point where New Zealanders are making something from that, then you're starting to cook."
The difficulty, he says, is deciding who gets that money - and it definitely shouldn't be exclusive to Māori.
"Not exclusively, that's for sure. You own it as much as I do or as much as Amanda or Mark [Gillies and Richardson, AM Show co-hosts] does. That's my position."
Then-Finance Minister Steven Joyce said a water tax would harm the environment, rather than help it.
Ms Davidson said she wasn't sure how many foreign companies were buying New Zealand land just to get access to water, but one was too many.
"Just one company in every community causes a lot of anxiety and issues not just for that community, but the whole country. Whenever one company does it, we have a problem."
She says it could take a year to get the Overseas Investment Act amended, because the Government wants to make sure it ends up with a "careful, good, robust law".