Rules around e-cigarettes should be relaxed so they can be more widely used and accepted in society, says a report by MPs.
Vaping is much less harmful than normal cigarettes and e-cigarettes should be made available on prescription to help more people quit smoking, it said.
The report also asks the government to consider their use on buses and trains. There is no evidence e-cigarettes are a gateway into smoking for young people, Public Health England said.
The report on e-cigarettes, by the science and technology MPs' committee, said they were too often overlooked by the NHS as a tool to help people stop smoking.
For example, it said it was "unacceptable" that a third of the 50 NHS mental health trusts in England had a ban on e-cigarettes on their premises, when there was a "negligible health risk" from second hand e-cigarette vapour.