The World Bank is alleged to have cut from a report research that suggests pollution causes hundreds of thousands of premature deaths annually in China.
Beijing has just reported its worst pollution for June in seven years
The move followed pressure from Beijing, which believes the material is too sensitive and could lead to social unrest, said the UK's Financial Times.
It said information was cut from the forthcoming report after requests from two Chinese government departments.
The World Bank told the BBC the final version had not yet been finalised.
But a statement added: "[A preliminary] version of the report did not include some of the issues that are still under discussion."
The Financial Times said the Bank report, entitled 'Cost of Pollution in China', found up to 760,000 people die prematurely each year in China because of air and water pollution.
High levels of air pollution in China's cities leads to 350,000-400,000 premature deaths, it said. Another 300,000 die because of poor-quality air indoors.
The newspaper article, quoting World Bank advisers and Chinese officials, also said research showing that there are 60,000 premature deaths each year because of poor-quality water was also left out of the report.
"The World Bank was told that it could not publish this information. It was too sensitive and could cause social unrest," one adviser to the study told the Financial Times.
It said the bank "reluctantly" agreed to take out the sensitive information.
The World Bank told the BBC that information for the report, which is being compiled in conjunction with the Chinese government, was still under review.
Between 1994 and 2004, China's greenhouse gas emissions grew by 4% a year
China currently depends on coal to meet two-thirds of its energy needs
It hopes to raise its use of renewable energy from 7% to 10% by 2010
China may overtake the US as the world's largest emitter of greenhouse gases by the end of this year
A World Bank spokeswoman refused to say whether or not statistics about premature deaths were amongst the information taken out of the initial version.
Despite the apparent dispute over figures, the preliminary World Bank report published in March suggests air and water pollution do lead to an increased number of deaths in China.
It also says the total cost of air and water pollution in the country amounts to about 5.8% of gross domestic product.
According to the Financial Times, China's State Environmental Protection Administration (Sepa) and its health ministry asked the World Bank to cut out the reference to the specific number of pollution-related deaths.
The BBC could not reach anyone at Sepa to comment on the issue.
But the government department is certainly aware of China's pollution problems. Last month it said about 60% of Chinese cities regularly suffer from air pollution and have no centralised sewage treatment facilities.
The final World Bank report is due to be released soon.
The organisation has previously said that China is home to 16 of the world's 20 most-polluted cities.