E-cigarettes marketed at teenagers contain potentially cancerous levels of artificial flavouring, new research has found.

The study of menthol and peppermint vapes revealed high concentrations of a carcinogenic additive called pulegone that US watchdogs recently banned in food.

Even moderate use of the increasingly popular products - available in the UK in supermarkets, specialist stores and online - put users significantly outside the “safe” threshold.

The tests were performed on e-liquids including the V2 Menthol and V2 Peppermint ranges, manufactured by WMR Products, a company since bought by Juul.

The pulegone additive, a constituent of oil extracts from mint plants, is believed to cause liver cancer if absorbed in high enough quantities.

While scientists behind the study do not know if pulegone is absorbed at the same rate through vaping as it is when eaten, they last night urged regulators to take precautionary action.

It comes days after Donald Trump promised to ban flavoured e-cigarettes in an effort to prevent children taking up the habit, and England’s Chief Medical Officer described vaping as “a ticking time bomb”.

Public Health England (PHE) encourages vaping as a means of quitting cigarettes and has argued that the habit is no more than five per cent as dangerous as smoking.