Revealed: The MPs who have smoked marijuana

On the day the Government finally announced its cannabis referendum plans, MPs have revealed if they've ever smoked it themselves.

Asked if she's smoked cannabis before, Prime Minister Jacinda Ardern said: "I was raised Mormon and then I was not Mormon - I let other people determine what that means."

When asked the same question, National MP Michael Woodhouse told Newshub: "Oh, yes."

Employment Minister Willie Jackson replied: "Of course."

But National MP Gerry Brownlee gave a definitive "no".

There were mixed views on the streets of Wellington on Tuesday, with one man named Andy telling Newshub he had a celebratory smoke.

Another person said legalising it would mean "everyone would just be stoned all the time", while another said it might take revenue away from gangs.

Newshub stumbled across a young man smoking a joint with his mate right under the Beehive, who said he doesn't believe in legalisation of recreational cannabis.

"I agree with decriminalising it, but I don't agree with legalising it because I think we will see the effects in 10 years' time - we'll be a country of dumb-bums."

Decriminalising cannabis isn't on the table - that's when using cannabis remains illegal, but instead of being prosecuted, you might be fined.

The referendum will be about legalising recreational cannabis, so cannabis will be legal, creating a regulated market, if New Zealanders vote in favour in 2020.

If New Zealanders vote to legalise cannabis, the legal age wouldn't be 18 like it is for drinking. You'd have to be 20 in order to legally use cannabis recreationally.

Justice Minister Andrew Little defended choosing the age of 20. He said the human brain is still developing up to the age of 25, "but if you put too high an age on it, you just encourage the black market".

People could grow their own cannabis, advertising would be banned, and cannabis could only be smoked on a licensed premise or private property.

Green MP and drug reform spokesperson Chloe Swarbrick said: "We do have a full-on health-based approach here that doesn't seek to make this product more accessible."

But the Opposition has come out strong against the referendum, with particular concern around cannabis-infused lollies.

National's drug reform spokesperson Paula Bennett said: "You're not going to get absolutely drunk on a couple of vodka soaked lollies but you can get absolutely wasted on a few concentrated marijuana."

And even if the country does vote to legalise cannabis, there's no guarantee a new government would change the law.

Asked if National would honour the result of the referendum, leader Simon Bridges said: "I simply don't know because there's no legislation."

So it could all go up in smoke.