China can prevent nearly 13 million tobacco-related deaths by 2050 by fully implementing a set of neglected anti-smoking policies it had already agreed to, researchers said Wednesday.

The estimated number of lives saved, more than the population of Greece, would result from a 40-percent lower smoking rate than that projected on current trends, said a paper in the British Medical Journal.

Without any change, it said, China risked accumulating more than 50 million tobacco deaths between 2012 and 2050 -- the largest burden of any nation.

But the toll could be reduced by more than a fifth through measures that include higher tobacco taxes, legislating for smoke-free areas and stricter advertising bans.

"The consequences of inaction are considerable," warned the paper that used computer modelling to predict the potential health benefits of a set of policies China had agreed to when it joined the World Health Organisation's Framework Convention on Tobacco Control (FCTC) in 2003.

"Without the implementation of the complete set of stronger policies, the death and disability legacy of current smoking will endure for decades in China."

The world's most populous nation accounts for about a third of the world's smokers, said the report. More than half of Chinese men smoke.

It was also the biggest tobacco producer.

The FCTC mandates a number of policies that include the creation of smoke-free environments, higher taxes, treatment for tobacco dependence, marketing bans and health warnings.

China has increased its tobacco tax on producers and wholesalers, but this has not translated into higher consumer prices, said the study.

It has legislated for a smoking ban on public transport, but advertising bans are "weakly enforced", it added.

China "has implemented few of the important policies," said study author David Levy of the Georgetown Lombardi Comprehensive Cancer Center in Washington.

The team estimated that a 75-percent tax on tobacco products would, on its own, prevent about 3.5 million deaths between 2015 and 2050, and a marketing ban would save another 2.15 million lives.

"Implementation of FCTC policies would alleviate a substantial portion of the tobacco-related health burden that threatens to slow China's extraordinary gains in life expectancy and prosperity," said the paper.

Under both scenarios, however, the absolute number of smokers and smoking deaths will continue to rise for several decades even as the percentages decline.

The UN's World Health Organisation (WHO) estimated last July that tobacco kills almost six million people each year, a toll that will rise to eight million annually in 2030.