Children as young as 11 have been smuggling electronic shisha pens into school in their pencil cases.

Several of the flavoured e-cigarettes, which come in bright colours, have been seized from pupils in Southwark and passed on to anti-fraud officers at HM Revenue and Customs for inspection.

The new playground fad was revealed by officers leading a crackdown on the smuggling of black-market shisha mix for traditional hookah pipes.

Shisha pens are similar to e-cigarettes and are popular in night clubs. They are said to be safe to use and an alternative to smoking tobacco through a pipe. Many schools have banned them.

Peter Millroy, HMRC’s assistant director of criminal investigation, said: “In the past smoking shisha was prevalent in certain groups but now it’s growing in popularity among younger people.

“It does shock me, I think any parent would be concerned. If you accept that smoking is harmful and smoking shisha is potentially harmful, the fact these are in the possession of children has to be a matter of concern. The fact children know what they are and have got them is obviously an emerging issue.”

The government has announced new legislation banning the sale of e-cigarettes and similar products to under-18s.

Experts say it is not yet known what harm the tobacco-free devices could inflict, and they could be damaging young people’s health.

Headteachers’ union NAHT this week called for parents to be banned from taking e-cigarettes on to school premises.