People trying e-cigarettes has doubled in number over two years, new research suggests.
Researchers studied at the use of the liquid devices across the European Union between 2012 and 2014.
In the UK, the proportion of people who had tried the electronic cigarette increased from 8.9% to 15.5%, the Imperial College London team found.
Meanwhile, in the EU, there was an average increase of 7.2% to 11.6%, according to the study, published in the journal Tobacco Control.
Data from 53,000 people in the EU showed that France had the highest e-cigarette use, with one in five saying they had tried them.
Portugal was the country with the lowest number of people who had tried e-cigarettes.
Lead author Dr Filippos Filippidis from the School of Public Health at Imperial 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".
The research shows that the proportion of people across the EU who considered e-cigarettes dangerous had also nearly doubled, from 27% to 51%.
The benefit of e-cigarettes to the nation's health remains in question, but a recent report by the Royal College of Physicians suggested it should be promoted as a substitute for e-cigarettes.