Because vaping has only become relatively widespread in recent years, there is a dearth of robust evidence indicating to what extent, if any, the practice is harmful in itself.

However, some scientists have said that e-cigarette smoking is, at most, five per cent as harmful as traditional smoking, with policy makers favouring e-cigarettes as a means of giving up tobacco.

Martin Dockrell, tobacco policy manager, Public Health England, added: "The findings in this study suggest that in terms of protecting children we are broadly getting the balance right in the UK.

"We have a regulatory system that aims to protect children and young people while ensuring adult smokers have access to safer nicotine products that can help them stop smoking. This includes a minimum age of sale, tight restrictions on marketing, and comprehensive quality and safety requirements. We will continue to monitor the trends in e-cigarette use alongside those in smoking."

Deborah Arnott, chief executive of the campaign group Action on Smoking and Health, said: "A small proportion of young people do experiment with e-cigs, but this does not appear to be leading to regular vaping or smokingin any numbers, indeed smoking rates in young people are continuing to decline."