An Auckland principal says underage vaping is an epidemic and flavoured vapes need to be banned.

Auckland Grammar's Tim O'Connor believes they're targeted at young people, despite being R18 products.

He guesses more than half his junior school is giving them a go, and stood down a dozen boys just last week for using them.

Tim O'Connor told Heather du Plessis-Allan they have banned students from a local fast food joint where they've been doing vape deals.

He says they are finding someone over 18 loitering at Burger King and getting them to buy their vapes, for a $5 cut.

"I stood down 12 boys from a year nine class just last week for vaping.

"The majority of these products contain nicotine and carcinogens, and they should be banned."