Cigarettes made by the US company Marlboro contain a significantly higher level of a cancer-causing chemical than most other foreign brands, US scientists say.

The Center for Disease Control and Prevention in Atlanta, Georgia, compared the level of the carcinogen nitrosamine in Marlboro cigarettes - chosen for their availability across the globe - with local brands in 13 other countries, including Japan and Germany.

It found that in 11 of the countries, the local brands had much lower levels of the chemical than Marlboro cigarettes, in some cases less than half the amount.

CDC officials said that the higher levels were the result of the way tobacco in US cigarettes is cured and blended.

'Reducing harm'

The results, published in the Nicotine and Tobacco Research journal, could indicate that it is possible for manufacturers to lower the levels of the nitrosamine carcinogen in cigarettes, report author David Ashley told the Associated Press news agency.

Philip Morris USA, which produces Marlboro cigarettes, said that it was working with US tobacco growers to reduce the amount of the carcinogen in its product.

'We're trying to find a way to reduce the harm associated with our products by reducing the level of harmful constituents that smokers inhale,' spokesman Brendan McCormick said.

'Reckless disregard'

However the CDC warned that nitrosamines are not the only carcinogen found in cigarette smoke, and said that reducing the level of one substance alone 'does not guarantee a less hazardous cigarette'.

And campaigners said that the study proved the cigarette industry had done little to remove harmful chemicals from cigarettes.

'[The] study is just the most recent example of the tobacco industry's reckless disregard for the health of smokers and yet another compelling reason why cigarettes need to be regulated by the federal government,' President of the Campaign for Tobacco-Free Kids Matthew Myers told Reuters news agency.

More than 400,000 people in the US die each year from diseases caused by smoking, and it is the leading preventable cause of death in the nation, according to CDC statistics.