E-cigarettes are battery-operated products that turn nicotine into a vapour inhaled by the user.
The Medicines and Healthcare Products Regulatory Agency said in a statement Wednesday it would treat e-cigarettes as medicines, "so that people using these products have the confidence they are safe, are of the right quality and work."
E-cigarettes and other nicotine products will be licensed in the U.K. from 2016, giving manufacturers time to ensure their products comply with all standards for medicines. The U.K. regulator says e-cigarettes aren't recommended for use until then, but it won't ban them entirely.
"While it's best to quit completely, I realize that not every smoker can and it is much better to get nicotine from safer sources such as nicotine replacement therapy," Britain's chief medical officer, Sally Davies, said in a statement. "It's only right (e-cigarettes) are properly regulated to be safe and work effectively."
Cigarettes are exempt from the regulation.
Last week, Britain's independent health watchdog said smokers unable to go cold turkey should be encouraged to use nicotine products like gum and patches to help them cut down. It hadn't recommended e-cigarettes, because they weren't yet regulated. Experts say smokers are at risk from the toxins and tar in cigarettes, not the nicotine.
Smoking is the biggest cause of preventable deaths in England, killing about 80,000 people every year. Once e-cigarettes and other nicotine products are licensed by the U.K. regulator, they will be available for sale as over-the-counter medicines. Britain said it will now push for European law to recognize nicotine products as medicines.
Some manufacturers said they were concerned about the new classification. Damien Scott, commercial manager of e-cigarette maker SKYCIG, said the products have been self-regulated to ensure they meet consumer standards.
"Medical regulation, which could restrict access to these lifestyle products, is entirely unjustified," he said.
In the U.S., the Food and Drug Administration announced in 2011 that it would regulate e-cigarettes as tobacco products and won't try to regulate them under stricter rules for medical drug-delivery devices following a legal battle.
The FDA, however, plans to assert regulatory authority over the fast-growing category in the near future.
E-cigarettes could also still be regulated as drugs or drug-delivery devices, if they are "marketed for therapeutic purposes" — for example, as a stop-smoking aid.
AP Tobacco Writer Michael Felberbaum contributed to this report from Richmond, Virginia.