Data from the Department of Health shows the proportion of smokers aged 14 to 17 had fallen to 2.1 per cent in 2018, but had since risen to 6.7 per cent.

The data also revealed one in seven teenagers in March was a regular e-cigarette user. Less than one in 100 teens vaped in 2018.

That has left experts worried vaping has undone the hard work of anti-smoking campaigns in the early 2000s.

“One of the biggest worries in public health at the moment is that widespread vaping will reverse our amazing progress in reducing smoking in children and adolescents in Australia,” Prof Emily Banks said on Friday.

The ANU academic said studies showed vapers were three times more likely to pick up smoking than non-vapers, pointing to “an alarming trend”.

Teenagers’ brains are still developing, which experts say makes them more vulnerable to addiction.

“For children and adolescents that can mean having difficulty sitting through a lesson or a meal with family because of craving and withdrawal symptoms, and the need to vape,” Prof Banks said.

The federal government has vowed to ban the import of all non-prescription e-cigarettes under a $234 million regulatory crackdown announced in the May budget, but no funding was set aside to enforce it.

E-cigarette liquids can contain more than 200 chemicals, including arsenic and benzene which are known to cause cancer.

Vape use has been confirmed to cause seizures, lung, facial and oral injuries, dizziness, loss of concentration, and nicotine poisoning.

Exposure to nicotine can exacerbate mood disorders and has been linked to negative impacts on cognitive performance and brain structure.