SHANGHAI, Aug. 20 ?A workers?rights group in the United States released a report today detailing what it called brutal conditions and illegal practices in Chinese toy factories, many of which supply some of the world抯 biggest brand-name toy makers, including Disney, Hasbro and Sega.

China Labor Watch, which is based in New York, said that it investigated eight Chinese factories over the last year and discovered widespread labor violations, including the hiring of under-age workers, mandatory overtime, unsafe working conditions and managers who engaged in verbal and sexual abuse.

In one instance, the group said a toy factory in southern China hired 1,000 junior high school students who had not yet graduated in the impoverished southwestern Guangxi province.

揝hort-sighted policies drive corporations like Hasbro to turn a blind eye to safety ? and to ignore the labor conditions in their supplier factories,?the group said in its report.

The report is being issued at a time of growing concern about the quality and safety of Chinese exports, and after a series of large toy recalls involving Chinese-made goods.

The Chinese government, however, has insisted that most Chinese exports are safe and of good quality, and multinational corporations say they have stepped up the monitoring and auditing of Chinese factories.

But some workers?rights groups say tainted and defective products are the byproducts of a factory system that allows big corporations to outsource to contractors here who routinely violate Chinese labor laws and cheat workers to reduce costs while also producing a profit.

Officials at Disney, Hasbro and Sega could not be reached for comment.

The report by China Labor Watch is only the latest in a series of reports issued by nongovernmental organizations over the last few years detailing worker abuse in Chinese factories.

Last June, a group of trade unions and nongovernmental organizations accused several Chinese companies that make merchandise for the 2008 Beijing Olympic Games of using under-age workers and forcing many to work overtime in unsafe conditions.

The Beijing Olympic organizing committee later revoked the license of at least one company that made Olympic merchandise, saying the company hired some under-age workers and did not have employee contracts.

Many other companies, including Apple and McDonald抯, have also been the subject of undercover investigations or expos閟 by journalists and workers?rights groups here.

Many companies, particularly toy companies, have independent auditors who make unannounced visits to factories that do contract manufacturing for them.

But critics say that auditors are sometimes fooled by factory managers, who are coached to deal with audits.