The number of people who have tried an e-cigarette has almost doubled in two years - and is only slightly lower than the proportion of people who regularly smoke.
In a new Imperial College London study of 53,000 people across Europe, researchers found the number of people who had tried vaping in the UK rose from 8.9 per cent of the population in 2012 to 15.5 per cent of the population by 2014.
Across Europe, the proportion of people who had tried an e-cigarette increased by 60 per cent from 7.2 per cent to 11.6 per cent over the same period. France was found to have the highest number of e-cigarette "ever users" - those who had tried an e-cigarette on one occasion or more - while Portugal had the lowest.
The study found that most of those who had tried e-cigarettes were either current or former smokers, although the number of non-smokers using the devices also grew over the period.
There are around 10m regular smokers in the UK, according to data released in November by ASH, equating to about a sixth of the UK's population.
A recent landmark study from the Royal College of Physicians, which said vaping should be widely encouraged as an alternative to smoking, concluded that the use of e-cigarettes was not a gateway to smoking.
It also found e-cigarette use is likely to lead to successfully quitting tobacco smoking that would not otherwise have happened.
However, in the latest Imperial College study, which was published in the journal Tobacco Control, the number of people across Europe who consider e-cigarettes as harmful also nearly doubled from 27 per cent to 51 per cent.
In putting together the research, scientists studied the use of e-cigarettes and attitudes to the smoking device across the continent between 2012 and 2014.
The research covered a representative sample of adults, above 15 years of age, from 27 European Union member states (excluding Croatia) taking at least 1,000 people from each country.
Dr Filipps Filippidis, lead author of the research, said:
This research shows e-cigarettes are becoming very popular across Europe – with more than one in ten people in Europe now having tried one of the devices.
However there is debate about the risks and benefits associated with e-cigarettes. For instance we don't know whether we may start to see diseases emerge in 10-20 years' time associated with some of the ingredients. We urgently need more research into the devices so that we can answer these questions.