E-cigarette use among teenagers rose nearly fivefold in four years, a study has shown.
The research questioned more than 4,400 adolescents and found 22pc were nicotine users.
Five per cent of Irish 15 and 16-year-olds smoked only e-cigarettes, nearly 8pc smoked tobacco cigarettes and 9pc smoked both.
Dr Andrea Bowe, a specialist registrar in public health medicine who headed the study, warned there were gaps in current legislation that enable e-cigarette companies to employ marketing and advertising tactics that appeal to younger audiences.
"E-cigarette companies are using flavours such as 'bubble gum' or 'cotton candy', which are undeniably youth orientated, and current legislation permits this," she said.
"The tobacco epidemic that took hold in the early 20th century was driven by many factors, including aggressive mass marketing, targeting of vulnerable youth population, denial by the tobacco industry regarding the health hazards of their products and gaps in legislation and policy which permitted all of the above to take place," she said.
"While e-cigarettes are not the same as tobacco cigarettes, there are many parallels."
The study found a sharp rise in e-cigarette use among young people from 2014 to 2018.
"The first Irish study of e-cigarette use among adolescents was conducted in 2014 and reported 3pc were users of e-cigarettes," Dr Bowe said.
"Four years later, am- ong more than 4,400 15 to 16-year-olds in the west of Ireland 14pc are current e-cigarettes users. That is almost a fivefold increase."
The study, published in a special Adolescent Substance Use and Related Harms issue of the International Journal Of Environmental Research And Public Health, found 26pc of the teenagers had a parent who smoked.
It is the first study to show that dual use - of standard tobacco and e-cigarettes - is the most prevalent behaviour among adolescent nicotine product users in Ireland.
Dr Bowe said e-cigarettes were initially advertised as a device to help smokers quit tobacco-smoking.
However, the majority of adolescents are not using them as a tool to quit a sustained smoking habit.
The study, carried out by the HSE's Department of Public Health West and Planet Youth West, found social norms were also a barrier to cigarette or dual use but not to e-cigarette-only use.
"Our study found those involved in team sports were less likely to use conventional cigarettes but were not less likely to use e-cigarettes", Dr Bowe said.
"The protective influence of sport participation on conventional smoking may be due to the widely accepted negative health impacts of conventional smoking and it may be a behaviour viewed as non-acceptable among athletes.
"E-cigarettes are marketed as a healthier alternative and perhaps appeal to a lower risk group who would not otherwise use conventional cigarettes.
"We must curb advertising which is targeting younger audiences."