Child development expert Nathan Mikaere-Wallis says no one should drink alcohol under the age of 18 because of the harm it causes.
Discussing parenting of adolescents and teenagers on Seven Sharp, Mr Mikaere-Wallis said young people who drink are not being kept safe.
"The reality is we don't keep them safe," he said.
"No one should really drink alcohol under 18," he said, admitting he started drinking at the age of 11.
Mr Mikaere-Wallis says the science shows that when under-eighteens do have more than a couple of drinks, their brains suffer.
"An adult male on average can take eight units an hour before he does any damage to the human brain. A teenager can take one unit an hour."
He advised parents to try to encourage their teen to sit on two or three drinks a night.
Seventeen-year-old Pierre suggested keeping to that limit might be easier said than done.
"Say you're at a party and all your friends are drinking and they're wasted, what's stopping you from getting wasted?" he asked.
Pierre admitted that if his parents tell him not to do something, that makes him "100 per cent" want to do it.
The minimum legal age for the purchase of alcohol in New Zealand is 18 years.
But New Zealand has no minimum legal drinking age, so although those under 18 are unable to legally buy alcohol themselves, they are legally permitted to consume it.