Gareth Morgan, leader of the new Opportunities Party, tried to explain his tax policy to Paul Henry on Thursday morning.

The policy proposes putting a minimum rate of return on all productive assets, including houses and land - so people could be taxed for owning the home they live in, or for having an expensive car.

Henry made it clear from the outset he didn't agree with the idea.

"I'm calling it an envy tax," he said.

"Oh ok. Well that tells me where you are," replied Morgan, and the battle was on.

"Essentially what you are doing is taxing things that are producing no revenue, but potentially could produce revenue," Henry said.

"Yeah, that's fair. That's totally fair," agreed Morgan.

"Doesn't that take away aspiration though?" asked Henry. "Why should I have to pay an extra tax because I choose to live in a five bedroom house rather than a two bedroom house?"

"It all depends if you want New Zealand to be fair or not, and you're telling me you don't give a toss," said Morgan.

The economist told Henry the existing system means there's a big tax loophole.

"If you've got a half-million dollar car, as opposed to... a $30,000 car don't you think that that's an asset that could be better put to use?"

"Well I think that's my choice, because I live in democracy," said Henry. "I've already paid tax because I paid more GST buying a more expensive car."

"You're telling me that you don't give a toss about New Zealand being fair. 'Pull up the ladder, Jack, and the rest of you can get stuffed'," Morgan said. "What sort of New Zealand values do you have, man?"

"My values are aspirational," retorted Henry. "I want people to aspire for greatness."

"You're just a tax loophole cowboy, that's all you are," said Morgan.

"I'm a tax loophole cowboy? Well, I referred to you this morning as a wowsery socialist," said Henry.

"I'm about making New Zealand fair," said Morgan. "You're self-centred and you don't give a toss about being fair in New Zealand."

The tax policy is the first of seven policies the Opportunities Party will reveal before going on a tour of the country to talk to voters.

The party is currently unregistered, and Morgan says: "We'll stay that way until we make the call whether we're going to bother."

Henry brought the interview to a close. "Enjoyable... It was fun," Morgan said.

"It actually was enjoyable... It was bloody entertaining, Gareth," Henry quipped.

Opinion is divided on social media, with many people on Facebook sharing their support for Henry or Morgan.

"Gareth Morgan and the rest of the namby pamby fairness equality faction need to wake up," Michelle Hosking wrote. "Life's not fair, it's what you make of it."

"I'd trust plain speaking, straight shooting Gareth Morgan any day over an opinionated, done nothing for nobody but himself, narcissist broadcaster like whatshisname Henry who," Grant Warren posted.

Jared English shared some detail on the policy itself: "People are forgetting that by the introduction of this tax it will lower the amount of income tax you pay on your wage putting more in your pocket each week. It's designed to tax those who have multiple investment properties who negative gear those investments to limit their withholding tax."

Watch the video for the full interview.

Newshub.