Despite years of anti-smoking measures being encouraged across the world, most developing countries have low quit rates, according to the study in The Lancet medical journal on Friday - and tobacco is likely to kill half its users.

There are wide differences in the rates of smoking between genders and nations, as well as major disparities in access to effective anti-smoking policies and treatments.

"Although 1.1 billion people have been covered by the adoption of the most effective tobacco-control policies since 2008, 83 percent of the world's population are not covered by two or more of these policies," said Gary Giovino of the University at Buffalo School of Public Health and Health Professions in New York, who led the research.

Such measures include legislation in some developed nations banning smoking in public places, imposing advertising bans and requiring more graphic health warnings on cigarette packets.

The findings come as the world's leading tobacco firms, British American Tobacco, Britain's Imperial Tobacco, Philip Morris and Japan Tobacco lost a crucial legal appeal in Australia this week against the introduction of plain tobacco packaging.

Australia's planned "no logo" laws are in line with World Health Organisation (WHO) recommendations and are being watched closely by Britain, Norway, New Zealand, Canada and India, which are considering similar measures to help fight smoking.

Tobacco kills up to half of its users, according to the WHO. Smoking causes lung cancer, which is often fatal, and other chronic respiratory diseases. It is also a major risk factor for cardiovascular diseases, the world's number one killers. Other forms of tobacco use include snuff or chewing tobacco.

Giovino said his findings "reinforce the need for effective tobacco control".

301 MILLION CHINESE USE TOBACCO

Using data from Global Adult Tobacco Surveys (GATS) carried out between 2008 and 2010, Giovino's team compared patterns of tobacco use and cessation in people aged 15 or older from 14 low- and middle-income countries. They included data from Britain and the United States for comparison.

They found disproportionately high rates of smoking among men - at an average 41 percent versus 5 percent in women - and wide variation in smoking prevalence between GATS countries, ranging from about 22 percent of men in Brazil to more than 60 percent in Russia.

Rates of female smoking ranged from 0.5 percent in Egypt to almost 25 percent in Poland. Women in Britain and the United States also had high smoking rates, at 21 percent and 16 percent respectively.

The study found that around 64 percent of tobacco users smoke manufactured cigarettes, although loose-leaf chewing tobacco and snuff were particularly common in India and Bangladesh.

With an estimated 301 million tobacco users, China has more than any other country, closely followed by India with almost 275 million. Other countries included in the study were Bangladesh, Mexico, Philippines, Thailand, Turkey, Ukraine, Uruguay and Vietnam.

The researchers said the rise in tobacco use among young women was of particular concern.

In a commentary about the study also published in The Lancet, Jeffrey Koplan from Emory University in the United States and Judith Mackay from the World Lung Foundation in Hong Kong called for more investment in tobacco control measures, saying current under-funding was "extraordinary".

In low income countries, they said, for every $9,100 received in tobacco taxes, only $1 was spent on tobacco control.

The WHO says tobacco already kills around 6 million people a year worldwide, including more than 600,000 non-smokers who die from exposure to second-hand smoke.

By 2030, if current trends continue, it predicts tobacco could be killing 8 million people a year.

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