Vaping has been linked to 200 health problems including heart disease and pneumonia, a watchdog has revealed.
The Medicines and Healthcare Products Regulatory Agency (MHRA) said there have so far been 74 health complaints suspected to have been caused by e-cigarettes.
Of these, 49 were officially classified as 'serious'.
But now it seems the number could be as high as 200, according to a dossier from the regulator seen by the Sunday Times .
Experts are now calling for a national system to record problems associated with e-cigarettes.
It comes as former factory worker Terry Miller became the first sufferer of lipoid pneumonia - when fat particles enter the lungs - that was attributed to vaping.
There have been 13 deaths attributed to vaping in the US.
Mr Miller, 57, from Gateshead, died in 2010. An inquest was called after doctors found oil in his lungs and a coroner recorded an open verdict.
His widow Glynis has since criticised UK health watchdogs for their claims about the safety of e-cigarettes.
Public Health England supports vaping as a route to help people quit smoking and has claimed that vaping is 95% less harmful than smoking.
It has come under fire from some academics who say the organisation is wilfully ignoring mounting evidence that vaping is harmful.
Dr Gareth Walters, a consultant in occupational and interstitial lung diseases at the University Hospitals Birmingham NHS Foundation Trust, said there is not enough information at the moment to assess the risk of vaping.
In the US, 13 people have died and 805 people have confirmed or probable cases of lung injury associated with vaping.
E-cigarettes are currently banned in Brazil, India, Thailand, Cambodia and Singapore.
