PARIS, France?Makers of electronic cigarettes are reporting strong growth in sales as anti-tobacco laws force European smokers into the cold streets, but campaigners say the device is undercutting health efforts.

Spain joined Sunday the ranks of countries that have outlawed smoking in enclosed public space after a wave of similar legislation across Europe.

For the makers of electronic cigarettes, which simulate the sensation of a cigarette and can contain nicotine, the traditionally heavy smoking nation marks a potentially lucrative market for their much-criticized product.

"We have seen sales grow by 30 percent each year since 2007 when we launched our product," said a spokesman for EdSylver, one of the leading manufacturers of the product invented in China in 2004.

Manufacturers such as EdSylver say the plastic cigarette is not harmful for the smoker or people around them, but this claim is rejected by health experts.

At a World Health Organization conference in Uruguay in November, one of its leading anti-tobacco experts Eduardo Bianco said electronic cigarettes "sabotaged smoking prevention efforts," which were designed to encourage people to quit.

The plastic cigarettes function as mini aerosols, releasing artificial smoke with or without nicotine.

"I am very happy with it, I want to repeat the feeling of smoking, without the harm of nicotine," said one Parisian user.

Professor Yves Martinet, head of the French National Committee Against Tobacco, said the electronic cigarette was a rip-off.

"This product offers no medical support for quitting smoking, there are some countries that have banned it," he said.

"For the moment, this product has not been evaluated in a scientific way," he said.

The French national office for smoking prevention said the purpose of the electronic cigarette was "ambiguous," and condemned its sale in pharmacies.

The office said the products were presented by manufacturers both as "an aid to quitting and a product which would allow smoking in enclosed spaces."

Tobacco sellers meanwhile reject manufacturers' claims that sales of the device are taking off.

"It doesn't sell at all, some of our members still have stocks from last year," said Gerard Bohelay, the head of an association of tobacco retailers in the French capital.