Under new regulations e-cigarettes will be licensed as a medicine from 2016.
Despite a move by some countries (such as France) to ban e-cigarettes, the UK currently has few restrictions on them.
The Medicines and Healthcare Products Regulatory Agency says it will regulate e-cigarettes as medicines when new European tobacco laws come into force.
Research suggests around 1.3m smokers and ex-smokers in the UK use the products, which are designed to replicate smoking behaviour without the use of tobacco.
Jeremy Mean of The Medicines and Healthcare Products Regulatory Agency (MHRA) said the government had concluded that e-cigarettes currently on the market do not meet appropriate standards of safety, quality and efficacy.
He said “levels of contamination” had been found in the products and some were poorly manufactured.
There will be no compulsory licensing of the products until 2016 but until then they are not recommended for use, he said.
“We can’t recommend these products because their safety and quality is not assured, and so we will recommend that people don’t use them,” he told a news conference.
The MHRA had decided not to ban the products entirely but to work towards a position where they are licensed, he added.
“Smoking is the riskiest thing you can do – we want to enable people to cut down and quit – we don’t think a ban is a proportionate action.”
Once licensed, e-cigarettes are expected to remain on sale over-the-counter in the UK.
In some countries, such as New Zealand, e-cigarettes are regulated as medicines and can be purchased only in pharmacies.
Click here to watch a short clip via BBC News.
In Warwickshire there is a free Stop Smoking Service for people wishing to quit. For help and advice on stopping smoking call 0800 0852917, text LIFE to 80800 or visit smokefreewarwickshire.org