Kiwis will be apologising to their kids for legalising marijuana - Paula Bennett

National Party drug spokesperson Paula Bennett says Kiwis will be apologising to their kids in 30 years if the country decriminalises marijuana.

Ms Bennett was speaking to The AM Show about plans to hold a nationwide referendum on the decriminalisation of marijuana for personal use.

She's not sure about which way she would vote because she doesn't know what kind of regulatory regime would be installed, but she's certainly not a fan of the drug.

"I'm yet to meet someone who's incredibly successful and having a great life that smokes dope every day," she told host Duncan Garner.

Her main concern is the effect on young people, saying marijuana kills brain cells.

A Dunedin study of more than 1000 people found lowers IQs in participants who became dependent on marijuana by the age of 18.

But later research disputes the findings, with some studies suggesting the lost IQ could be linked to a number of other factors as well.

Aside from the matter of brain cells, there is other evidence marijuana has detrimental effects on the brain.

Researchers from Christchurch and Dunedin say it could lead to educational delay and increased risk of psychotic symptoms, among other things.

Ms Bennett agreed alcohol is bad too, but said now is the chance to avoid giving people as much access to marijuana as they do alcohol.

"Knowing what we know now would we really go down the tracks that we have, and we have a chance to do that with marijuana."

Garner, who has already admitted he's not in favour of decriminalisation, questioned what people would say to their kids 30 years in the future if the drug is decriminalised.

But Ms Bennett said she already knows.

"Sorry. We [will] say sorry."

Newshub.