Labour leader Andrew Little said on TVNZ 1's Breakfast this morning that he had tried cannabis on "two or three occasions", but wants a "credible answer" to possible health issues for young people if New Zealand was to go through drug reform or liberalisation.
"We do need to have a close look at what's happening here and around the world," he said.
"What underlies the drug use is usually problems with addiction. We have a massive shortage of supply of, for example, addiction counselling."
He also said the effect drug use had on the brain of younger people was an influencing factor in liberalisation.
"Even reasonably modest cannabis use can have long-term negative effects on the human brain," he said.
"The big thing for me is, if you liberalise or decriminalise what does that mean for access for younger people?"
"We've got to make sure we're not creating other health problems by greater liberalisaton."
Yesterday, Prime Minister Bill English said he had not smoked cannabis.