Increase the drinking age to 20: Gareth Morgan

Gareth Morgan says he knows some young people will oppose the change. New Zealand Herald photograph by Mark Mitchell.

The alcohol purchase age would be 20 years and booze prices would jump by an average of 10 per cent under policy by Gareth Morgan's political party.

The Opportunities Party today released its alcohol policy.

It says the excise tax increase will generate an extra $300m a year, which can be put into drug and alcohol treatment, and youth mental health support.

Morgan said he knew some young people would oppose the policy.

"But they can rest assured Top's soon-to-be-released youth support package will more than make up or anything they feel they have lost through this change.

"One doesn't need to be a policy analyst to see that lowering the age of purchase has effectively lowered the socially acceptable age at which young people start drinking. Along with that has come an increase in harm to young people through motor vehicle accidents, teen sexual assault and mental and other health issues."

Morgan said particularly concerning was the number of young women becoming problem drinkers, and the risks that went with that.

In releasing the policy, Top said reducing the minimum age of alcohol purchase from 20 to 18 years in 1999 had contributed to increased alcohol-related harm. This was worsened by the fact brains were still developing at age 18 and 19.

Top has previously announced policy to make cannabis legal for anyone over 20, under a system regulated by the government in which growers and sellers would need licences, and a minimum price would be set.

Market research commissioned by Top showed cannabis law reform was the most pressing issue for voters aged 35 and under.

Top uses a "deliberative democracy" approach to decide some policy, which sees members submit on an issue and provide evidence to back their position.

Morgan announced the formation of Top in November, and will need to win 5 per cent of the party vote to enter Parliament after September's election.

At the 2014 election, Craig's Conservative Party received 95,598 votes and still fell short of getting an MP into Parliament, gaining just under 4 per cent of the party vote.