The evidence is clear that lowering the age to 18 increased alcohol-related harm, says Gareth Morgan.

Gareth Morgan wants to raise the alcohol age to 20 and increase the price of booze.

Morgan released his The Opportunities Party (TOP) policy on alcohol on Tuesday morning.

It calls for a 10 per cent increase on the price of alcohol through a larger excise tax and a bump in the purchasing age back to 20 from 18.

The purchasing age was lowered to 18 from 20 in 1999.

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"It was lowered in 1999 to appease the alcohol lobby, and we were promised at the time that if evidence showed harm went up after the change they would reverse it," Morgan said.

123rf Stronger cheaper drinks like RTDs would be the worst hit by the price-hike.

"All of the evidence, all of the reports, have pointed unambiguously to harm going up."

Research showed the lowering of the age had resulted in the "de facto" drinking age falling to between 14 and 17, Morgan said.

"The data is showing us that in secondary schools six out of ten students are drinking. Nearly half of them consume more than five drinks in each session. And one in five are saying the aim to get drunk. That's where the problem is."

Raising the age to 20 would bring up the de facto age to around 18, Morgan said.

The price hike would not apply to all alcoholic drinks equally. It would tax the amount of alcohol in each drink, meaning cheap but strong RTDs would be the hardest hit.

"The ones that the youth and alcoholics binge on would feel it the most. It's on a pure alcohol basis," Morgan said.

The forecast $300m in extra tax this would bring in would be used to fund youth mental health support and addiction treatment.

"The combined harm for alcohol is three times greater than the combined harm from all other drugs," he said.

He cited government research which showed alcohol was responsible for four per cent of all avoidable deaths - between 600 and 800 a year.

"There will be push-back from the lobby and from the alcohol industry, but I expect that families would be highly supportive."

He said any age rise would be phased in so those already of drinking age would not lose out.

Prime Minister Bill English said the Parliament had debated the issue many times and he could not see it being keen to debate it again.

"I don't think there's been a strong case made for raising the drinking age," English said.

Revenue Minister Judith Collins said she had "tried to" raise the age when she was Justice Minister but had not had much luck.

Labour health spokesman David Clark said the drinking age was not a priority for his party.

"We want to make sure the services of support are properly funded. We know that works," Clark said.

Alcohol and drug issues went to a conscience vote for Labour and National.

Last time the issue came up Clark had voted for a "split age" - with bars and pubs still being able to sell booze to 18-year-olds but not liquor stores or supermarkets.

"My experience is that the pubs in town look after people pretty well - they exercise a duty of care," Clark said.

"The reality is young people are going to get a hold of booze one way or another, and I would prefer they did it in a controlled environment."

Justice Minister Amy Adams voted for the split-age as well, and retained that preference.

ACT leader David Seymour said he would "absolutely" keep the age at 18.

"If you want to be evidence-based, binge drinking is lower amongst today's youth than it was 20 years ago, rates of consumption of alcohol have gone down over the last 20 years, this is just another beat-up on young New Zealanders," Seymour said.

Seymour said he "probably" drank more than today's youth in his prime.

"Some of these kids today are a little bit lightweight."

National's Chris Bishop, who campaigned to keep it at 18 when he was at university in 2006, said the evidence actually showed Morgan was wrong.

"Basically I think he's just on a populist crusade hunting for media coverage, trying to scapegoat 18 and 19-year-olds."

"I also think there is a civil rights issue there too. If you can vote at the age of 18, can get married at the age of 18, can die for your country at the age of 18, you should be able to drink."

"Every six or seven years it seems to pop up, I think it is fairly popular with the public but its wrong-headed policy."

The Opportunities Party polled at 0.8 per cent recently, higher than any other minor party but far from the five per cent needed to enter Parliament.

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