Experiments administered by scientists demonstrate that vapours produced by e-cigarettes are not harmful to human lungs.

The research, funded by British American Tobacco, suggests that inhalable nicotine vapour could be as innocuous as fresh air.

To get these stunning conclusions, scientists constructed a “smoking robot” to expose replicas of lung cells to regular tobacco smoke, vapours from two e-cigarette brands and fresh air.

After six hours of tobacco smoke, the fake lung cells died.

However, when the cells were tested by “aggressive and continuous” vapour, the damage was “similar to that of air”.

“Despite the limitations of the research, it adds additional evidence to support the contention that vaping is a lot safer than smoking,” said Dr Michael Siegel, professor in the department of community health sciences at Boston University’s school of public health.

Siegel also called for public health bodies and anti-tobacco movements to encourage smokers to switch to vaping.

E-cigarettes continue to surge in the UK, helping thousands quit and improving the health of smokers.