Russel Norman says he is more of a disciple of market forces than is the National Party.
The major issues of sustainability can be solved by setting the right incentives and prices, he says.
Labour and the Left have generally argued for a more interventionist approach, while National says it favours creating the conditions for the economy to grow.
However, Norman said he was a strong believer in market solutions.
"If you look at the Greens, or at least our policies, they are pro-market," Norman said.
"Lower company tax rates, price signals for carbon - let the market resolve the issue."
The Green proposal for a Green investment bank, which would use state capital to invest in renewable companies "is identical to what [British Prime Minister] David Cameron set up for the UK".
Norman favoured retaining the current GST structure because it was simple.
"GST? You name it. The fact is my view, and the Green Party policy, is that markets are a really good solution to the big challenges we're facing in sustainability, so that's why we're very pro the use of market forces, whereas National are into state intervention, which is the exact opposite of the predominant discourse, right?" he said.
"You just need to get the prices right, get the incentives right."
Norman said National chose which motorways to favour for political reasons, without properly conducting cost-benefit analyses, while the approach to tax credits was a test "of whether [Economic Development Minister] Steven Joyce likes your company".
"Everyone says National doesn't pick winners ... but if you look at what they're actually doing, they're not pro-market, they're Muldoonist."
Norman said the environment was the biggest area where the "user-pays" model was not applied.
"Currently they [polluters] get to externalise their costs of carbon and water pollution on to other people," Norman said.
"Someone else has to pay it. If you look at all the money the Government has been throwing at water cleanups, at the same time as saying 'we're not going to constrain dairy companies from polluting rivers' but the taxpayers are going to foot the bill to clean up all these rivers.
"Hang on, you've just externalised their costs onto us [taxpayers]. That's not OK. You've got to clean up your own act. You don't get the right to let the taxpayer clean up the mess you created, whether its water pollution or carbon, and it's quite the opposite in my view. You've got to internalise those costs."
Current polling suggests that for Labour to have any chance of forming a government, it would need the support of both the Green Party and NZ First, as well as potentially Internet-Mana.
Norman said the party had no bottom lines heading into the election, but raised its plan to impose a fixed price for carbon (Labour proposes improving the current emissions trading scheme) as a potential sticking point.
"We want to put a proper price on carbon ... Anyone who thinks an international price on carbon isn't coming down the line is just dreaming. I think National is locking us into an economy which will have a whole bunch of stranded assets."
Norman said it was more difficult to assess the policies of NZ First and where any sticking points might be, because unlike Labour and the Green Party, it had not produced a fully costed package.
However, he raised concerns about NZ First leader Winston Peters' plan to strip GST from basic food items and council rates because of concerns about the impact of tinkering with GST.
"We've supported that position [of maintaining GST] all the way through. So when Labour wanted to remove GST off fruit and vege, we didn't support it. We didn't oppose it, we said we'd look at it, but we weren't big supporters of it because, really, it's not going to benefit the people you want to target, and it just complicates the system," Norman said.
"GST off rates? It's [a cost of] $700 million a year for that, and we don't have $700m in our budget for that, so we've just said maintain the status quo. It works. It's not perfect but it's relatively clean. There are exceptions to be fair under the current system, but, you know, people understand the current system."
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