National Party MP Paula Bennett believes there is "a high risk of normalisation" and that cannabis usage could increase in young people if the drug is legalised following the referendum at this year's election.
However, in a debate on TVNZ1's Breakfast this morning, Greens MP Chlöe Swarbrick countered the argument, saying evidence does not suggest that - in fact, the opposite was shown in Canada - and that it is important to regulate the now-illegal substance.
According to a UMR poll released by the Helen Clark Foundation and the New Zealand Drug Foundation yesterday, 48 per cent of people are in favour and 43 per cent are opposed to legalising the drug. A previous poll in February by the same operators had support at 46 per cent.
Ms Bennett, who opposes the Cannabis Legalisation and Control Bill, used the speed limit on New Zealand roads as an analogy. Just because plenty of people still speed, just as many people use cannabis, it doesn't mean politicians should make speeding legal.
"There's a whole lot of 'just because people have done it', you then go and completely turn it upside down."
However, Ms Swarbrick responded, "on the speeding one, I get this one relatively frequently. We don't ban cars, we regulate how people are supposed to use those cars and this is the difference between an approach that's sensibly regulates and says, 'Hey, if you step outside the bounds of what evidence base says, puts other people in danger or puts yourself in danger, don't do it.'
"If you decriminalise, you remove criminal penalties from the people who are using the substance but you're completely silent on the issue of where they get that cannabis from. So you're still able to supply to young people, there's no potency controls and there is the, kind of, proliferation of the substance under the black market."
Ms Swarbrick also said that 80 per cent of adult Kiwis had used cannabis, but under the current laws it means some people who get caught may face job loss, impediments to travel, future education and work, while others who don't get caught can go on to be successful politicians such as herself.
"We've all admitted that prohibition simply isn't working," she said.
However, Ms Bennett said there was "so much wrong with that" argument, adding that changes already made by the current Government meant police had discretion in arresting for the use of cannabis.
"We're not criminalising people, no we're not. That's just where I think the misinformation is doing a discredit," she said.
"I believe that there is a high risk of normalisation and that it [usage] could go up in our young people [if legalised]."
"That's not what the evidence says," Ms Swarbrick responded. "The evidence shows in states across the US that it has remained stagnant and in Canada it's gone down."
This week, the Government launched a non-partisan website that will help voters figure out whether they'll vote yes or no to cannabis in the referendum at this year's election.
The Prime Minister's chief science adviser Juliet Gerrard, who is running the site, told Breakfast on Tuesday that the website will give a well-rounded overview of both sides of the debate.