BBC Consumer Affairs Correspondent June Kelly: "The government is worried that this will encourage young people to smoke"

Anti-smoking campaigners say the additives are designed to make cigarettes more attractive to children. They cite the similar way alcoholic soft drinks, or "alcopops", were marketed to youngsters.

The government made cutting smoking among young people a key focus of its White Paper on Tobacco, published in December.

Health Secretary Frank Dobson said he wanted to see the numbers of teenage smokers fall from 13% to 9% by 2010.

The last decade has seen a 70% rise in teenagers smoking compared with a drop in the number of older people who smoke.

Mr Dobson says most people begin smoking when they are young.

More addictive

A coalition of health groups, including the British Heart Foundation and the Royal College of Physicians, wrote to the government last autumn, pointing out that over 600 additives can legally be added to tobacco products.

In a statement they said: "Additives to tobacco products present profoundly different problems to food additives as they may cause harm by increasing the use of tobacco."

They say the additives may appear harmless in themselves, but can increase the addictiveness of cigarettes.

Smoking is linked to many forms of cancer, heart disease and other illnesses

For example, chemicals can enhance the alkaline content of smoke, which will increase the nicotine hit, making it more addictive.

Sweeteners such as sugar can also be added to cigarettes, making them more appealing to young people.

"There can be no justification for such additives," the statement read.

The BBC's June Kelly: "The government wants smokers to know more about what they are inhaling"

The campaigners have been calling on the government to introduce a regulatory framework on additives.

They say a 1997 voluntary agreement is unlikely to be effective as it only applies to new additives and those which are toxic.

Dr Martin Jarvis of the Imperial Cancer Research Fund said he wants the government to force tobacco companies to reveal what additives are in particular brands of cigarettes and to show that they do not have a damaging effect on public health.

"We want them to justify their use of additives because we are concerned that they may not be toxic in themselves but could have bad effects from a public health perspective if they make it easier for people to inhale or make them more attractive to young people," he said.

Tobacco companies deny they have deliberately attempted to get young people hooked on smoking.