Non-smokers should never take up vaping, despite their being heart benefits for those who switch from tobacco to e-cigarettes, scientists have warned, following the most comprehensive study to date.

A trial which looked at the impact of moving from smoking to vaping found that within a month blood flow through a major artery had significantly improved and was around halfway back to the function of a non-smoker.

Although researchers could not say whether the effect would continue, if it did, smokers could see their risk of cardiovascular events such as heart attacks or strokes fall by more than 13 per cent.

Yet despite the benefit, experts from the University of Dundee said vaping was harmful, and experts warned that calculations made by Public Health England (PHE) suggesting it is 95 per cent safer than smoking were too simplistic.

Jacob George, Professor of Cardiovascular Medicine and Therapeutics at the University of Dundee, who led the trial, said: “It is crucial to emphasis that e-cigarettes are not safe, just less harmful than tobacco cigarettes when it comes to vascular health.

“They should not be seen as harmless devices for non-smokers and young people to try. However for chronic tobacco smokers there were significant improvements in vascular function within a month of switching from tobacco to an e-cigarette.”