BANGKOK, Thailand - Two of the world's largest tobacco companies, seeking to expand their sales in Asia, worked to undermine antismoking policies there by infiltrating a research institute in Thailand and funding another in China, researchers said yesterday.

The allegations in two separate studies come while tobacco companies are aggressively marketing cigarettes in the developing world as lawsuits and antismoking laws hit revenues in the West.

"As the high-income countries put more and more obstacles in the path of the cigarette companies, they have to look for new markets," said Edouard Tursan d'Espaignet, epidemiologist with the WHO's Tobacco Free Initiative.

In Thailand, Philip Morris, the world's largest cigarette maker, planted a scientist in the Chulabhorn Research Institute in Bangkok to try to get researchers to shift their attention away from secondhand smoking and toward other forms of air pollution, according to one study.

Public-health researchers from the University of Sydney and the University of Edinburgh produced the report by analyzing internal industry documents made public following litigation in the United States.

A second study alleges that British American Tobacco, the world's second-largest firm, provided funding in China for the Beijing Liver Foundation in a campaign to shift focus away from links between smoking and ailments such as liver disease.

Both companies denied the allegations, which were presented online in the Public Library of Science Medicine journal. The two studies were partly funded by the National Cancer Institute in the United States.

Longtime antismoking advocate Stanton Glanz said the tactics were "part of long-running and continuing tactics by the tobacco industry all over the world." He called on the two Asian institutions to end their ties with the industry.

The University of Sydney's Ross MacKenzie, who cowrote the Thai study, said that tobacco companies had fought successfully to prevent the publication of ingredients used in their products in Thailand and worked in Cambodia to undermine advertising bans.

MacKenzie and the University of Edinburgh's Jeff Collin allege that Philip Morris scientist Roger Walk lectured and organized conferences at the government-funded Chulabhorn from the early 1990s through 2006.

The researchers say this allowed Philip Morris to develop relationships with key officials and scientists in efforts to discount the threat of secondhand smoke.

Spokeswoman Marija Sepic of Switzerland-based Philip Morris International - which was spun off by the Altria Group in the United States earlier this year - dismissed the documents as outdated and said the company never hid its affiliation with Walk.

Walk, who now works for Altria's Philip Morris USA unit, could not be reached for comment.

Chulabhorn's associate vice president, Jutamaad Satayavivad, said the institute was not aware that Walk worked for Philip Morris until about a decade into his tenure. She said that after seeing the study, institute officials plan to bar him because he was "not straightforward in sharing with us."

The other study alleges that London-based British American Tobacco used the Beijing Liver Foundation to lobby China's Health Ministry in a campaign to forestall smoke-free legislation.

The company provided training to industry, public officials and news media to spread its view that secondhand smoke is an insignificant source of pollution, it said.

"Despite the tobacco industry's public efforts to appear socially responsible . . . there is a fundamental conflict between the interests of tobacco companies and public health," said the Mayo Clinic's Monique E. Muggli, who conducted the study with four other researchers.

China's Health Ministry did not immediately respond to a faxed request for comment.

British American Tobacco spokeswoman Catherine Armstrong said it was illogical to suggest that any link the company has to a medical charity "was an attempt to divert attention away from smoking-related disease."