Tobacco manufacturers have been accused of adding substances to cigarettes to increase their addictiveness so that more people are hooked by the smoking habit.

Anti-smoking groups have called for a clampdown on the practice, claiming that current UK and EU regulation of tobacco additives is inadequate.

ASH and the Imperial Cancer Research Fund say that they have evidence - uncovered by a review of tobacco industry documents - that:

• Additives are used to make cigarettes that provide high levels of 'free' nicotine which increases the addictive kick of the product
• Additives are used to enhance the taste of tobacco smoke
• Sweeteners and chocolate are used to make cigarettes more palatable to children
• Eugenol and menthol are added to numb the throat to mask the aggravating effects of tobacco smoke
• Additives such as cocoa are used to dilate the airways allowing the smoke an easier and deeper passage into the lungs
• Additives are used to mask the smell and visibility of smoke that is not breathed in by the smoker

A spokesman for the manufacturers in the UK said the research was based on the situation in the US, and that in the UK 90% of cigarettes contained no additives.

But Dr Martin Jarvis, of the Imperial Cancer Research Fund, said: "Outside the tobacco industry no-one knows which additives are used in which brands.

"The tobacco companies' excuse for using additives is that they make low tar cigarettes easier to smoke.

"We know that low tar cigarettes are just as bad for you as regular cigarettes, so using additives can not be justified.

"As some additives can make cigarettes more addictive, tobacco companies are making it even harder for those smokers wanting to quit to succeed."

Uncovered a scandal

Clive Bates has called for tighter regulation

Clive Bates, director of ASH, said the research had uncovered a "scandal in which tobacco companies deliberately use additives to make their bad products even worse".

Mr Bates said: "Without telling anyone, they have been free-basing nicotine and engineering subtle changes to the brain chemistry of the smoker.

"The idea of taking an addictive product and making it more addictive is extremely disturbing."

The US State of Massachusetts has forced tobacco companies to disclose which additives are used in which brands and why.

The industry has responded by suing.

Dr Gregory Connolly, director of the Massachusetts Tobacco Control Program, said: "The tobacco industry's documents raise serious concerns about the way they have engineered cigarettes to be more addictive.

"We are starting to hold them to account in Massachusetts, and they really don't like it."

Tobacco industry denies claims

John Carlisle dismissed the claims that UK cigarettes are pumped full of additives

John Carlisle, director of public affairs for the Tobacco Manufacturers' Association, dismissed the claims as "nonsense and scaremongering".

Mr Carlisle said the research was based on the situation in the US, and that in the UK 90% of cigarettes consumed contained no additives at all. Those additives that were used came from a list approved by the government, and the majority of those items on the list were never used at all.

"This report is nonsense, a scaremongering tactic to try to frighten consumers," he said.

"We are doing everything that is asked of us by the government to ensure that we produce a product in which the UK consumer can have total confidence."

Mr Carlisle said that if anybody was unhappy with the additives that were legally allowable in the UK, then they should complain to government. He would not confirm that additives were not used to increase the addictiveness of cigarettes.