Advertisements for chocolate and bubble gum-flavoured e-cigarettes could attract children to try vaping, according to new research.
The research, carried out by the University of Cambridge for the Department of Health, examined concerns that the use of e-cigarettes among children and adolescents could lead to tobacco smoking.
The study found school children shown adverts for candy-flavoured e-cigarettes expressed greater interest in buying and trying them than their peers.
It is illegal to sell e-cigarettes and e-liquids to under-18s in the UK, but their use rose from 5% in 2013 to 8% in 2014, researchers from the university's Behaviour and Health Research Unit said.
Milica Vasiljevic, from the Department of Public Health and Primary Care at the University of Cambridge, said: "We're cautiously optimistic from our results that e-cigarette ads don't make tobacco smoking more attractive, but we're concerned that ads for e-cigarettes with flavours that might appeal to school children could encourage them to try the products."
The researchers said candy and liqueur-flavoured tobacco products were heavily marketed towards young people from the 1970s to 2009 when regulations were imposed.
E-cigarettes are now being marketed in about 8,000 different flavours.
The researchers said that the study supported moves for greater regulation of advertising for e-cigarettes, including rules that adverts must not be likely to appeal to under-18s.
New rules have been issued by the Committee on Advertising Practice but do not include explicit prohibitions on candly-like flavours.
They added: "The results of the current study support the imminent changes in EU regulations surrounding the marketing of e-cigarettes, but raise questions about the need for further regulation regarding the content of products with high appeal to children.
"More research is needed to examine both the short and long-term impact of e-cigarette advertising, as well as the link between e-cigarette use and tobacco smoking."
Professor Kevin Fenton, director for health and wellbeing at Public Health England, said the PHE was "cautiously optimistic" about the results that e-cigarette advertising does not make smoking tobacco more attractive.
He said: "The UK already has some of the strongest regulations on e-cigarette advertising, and these will be further tightened by new European regulations being introduced in May.
"Responsible e-cigarette marketing needs to recruit adults away from smoking and in the UK it has been effective in doing this. And there is no evidence that advertising has encouraged young people to take up regular vaping.
"It's important we recognise that flavoured e-cigarettes can appeal to adults as an alternative to smoking."