In a review of evidence on e-cigarettes commissioned by the government-backed authority Public Health England, experts said e-cigarettes could already be helping some 20,000 United Kingdom smokers a year to quit tobacco - and possibly many more.
Joyce Robins, of campaign group Patient Concern, told The Times that it was a bad idea to use up much-needed spaces in hospitals to create vaping areas.
The experts found two in five smokers have never tried an e-cigarette.
It also called on Britain's National Health Service to ensure e-cigarettes are available in hospital shops along with other nicotine replacement products such as gum and lozenges.
The review found that the use of e-cigarettes in the United Kingdom has plateaued over the past few years at just under 3m.
"A new Public Health England evidence review has indicated that e-cigarettes pose only a fraction of the health risks of regular cigarettes, and that they can be a valuable tool in helping people to quit smoking."However, "the number of e-cigarette users has plateaued at just under three million people in the UK", the website says.
The call comes from Public Health England, as part of an evidence update on the safety of tobacco alternatives which it says should be used more widely as quitting aids.
Smoking shelters are where patients and visitors go to for a cheeky fag.
PHE experts, writing in The Lancet, said: "Although not without risk, the overall risk of harm is estimated at less than 5% of that from smoking tobacco; the risk of cancer has been calculated to be less than 1%".
"We are saying no smoking anywhere on the grounds [of hospitals], no smoking in the smoking shelter - that shelter becomes a vaping shelter", said Martin Dockrell, tobacco control lead for PHE. Yet more than half of smokers either falsely believe that vaping is as harmful as smoking or just don't know.
"Anything that the [Medicines and Healthcare products Regulatory Agency] MHRA can do to make it easier for manufacturers we think would be helpful", said PHE health improvement director John Newton.
Academic Ann McNeill, professor of tobacco addiction at King's College London said: "When people smoke tobacco cigarettes, they inhale a lethal mix of 7,000 smoke constituents, 70 of which are known to cause cancer".
The stall could be down to smokers "incorrectly" believing vaping is as harmful as smoking.