Schools have banned the use of electronic cigarettes over fears they are being used by pupils to start smoking.
In an ironic new trend, children are turning to smokeless cigarettes, which are designed to help people give up the habit, before moving onto traditional ones.
Blatchington Mill School in Hove has written to parents warning them of the dangers after it decided to ban the personal vaporisers.
The fear is these cigarettes, which vaporise liquid nicotine, act as a stepping stone to the real thing and could be creating a new generation of smokers.
There are no age restrictions on buying them and they come in a variety of flavours.
They are proving popular at schools as they produce no smell and so it is difficult for the pupils to be caught in the act, unlike lighting up.
There are also versions without tobacco sold over the counter but guides on how to modify them to contain tobacco are easily available online.
One 14-year-old pupil in Year 9 at Blatchington Mill said: "Everyone thinks it's rebellious to smoke but it's the soft version of that, the one without any bad side effects.
“I know some people who have done it in class but haven't been caught because you can just waft away the vapour so no one knows.”
Both said they had not caught children in the act but that this was difficult to do as the electronic cigarettes were odourless, smokeless and battery powered.
Brighton and Hove City Council backed the ban by the schools but said it was awaiting national public health guidance on e-cigarettes.
Labour education spokeswoman Anne Pissaridou said the trend was clearly a “worry” and that the dangers needed to be highlighted.
The letter from Blatchington Mill said: “Electronic cigarettes, also known as E-Cigs, personal vaporisers or PVs, have been growing in popularity, especially amongst adolescents.
“Originally marketed as a way of quitting smoking, they are being increasingly targeted at a young market and scientific research has questioned their utility in helping to quit.
“Research has also found toxic chemicals in some E-cigs as well as the fact that they may be acting as a gateway into smoking, rather than a way of stopping.”
The British Medical Association highlighted the dangers of the “appearance, nomenclature, and the way they are used, as well as features such as flavouring and styling that are potentially highly attractive to children”.
It has called for tougher regulations on selling them so they do not reinforce cigarette brands as well as backing bans on the use of them.