Mark Richardson says former Prime Minister Helen Clark is wrong to think New Zealanders will opt for watered-down weed.
"It's not a health food - this is not kale, this is not spinach," Richardson said on Wednesday. "This is weed."
"If I'm going to buy weed I want St Heliers super skunk."
The Helen Clark foundation is launching a new research paper that says 'yes' to the 2020 cannabis referendum.
Clark said it's time for the drug to be regulated rather than criminalised.
"I think we ought to focus on getting the laws around it right and then we can focus on the health messaging," she told The AM Show.
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Richardson said Clark made some sense, but there is one thing he doesn't agree with.
"Where Helen's argument for me fell down, is that she seems to think that if this stuff is legal, we're going to go into the shop and ask for the watered down version."
The AM Show newsreader Amanda Gillies said the reality is, kids are likely trying it.
"Wouldn't you rather they go to the store and get it? Try maybe a watered-down version, have their hit, move on."
The foundation would also like to see all minor criminal convictions for cannabis expunged if it were to become legal.
"It's interesting because the teenagers I know, they're not really that into it," Gillies said.
"Vaping is their thing - that's what they're into."
The report also said big business needs to be kept from distribution, to avoid profit motives.
Richardson concluded cannabis is "not like meth".
"It doesn't come with this huge euphoric effect that will immediately hook you."