SINGAPORE — Chinese factories producing Olympic caps and hats are employing children, paying half the minimum wage and forcing employees to work seven days a week, according to a report by a group of overseas trade unions.

Several factories manufacturing official merchandise for the 2008 Beijing Olympics are getting 12-year-olds to work 15-hour shifts in unsafe and unhealthy conditions, according to the report by PlayFair 2008 group of unions and nongovernmental organizations.

Labor representatives including the Brussels-based International Trade Union Confederation said they want the International Olympic Committee to add employment conditions to licensing contracts. Beijing Games licensing may generate $70 million in revenue, according to the report.

“The horrendous conditions faced by Chinese workers working on Olympic products puts the IOC and the Chinese government to shame,” said Lee Cheuk Yan, general secretary of the Hong Kong Confederation of Trade Unions, in a statement. The Lausanne, Switzerland-based Olympic committee said it doesn’t manage production of Olympic-related products. Beijing 2008 organizers said they would investigate the factories.

“The IOC is committed to being a socially responsible leader of the Olympic movement that takes care of the Olympic brand in the best way possible,” committee spokeswoman Giselle Davies said in the statement. “It matters to us that sourcing is done ethically.”

According to the PlayFair 2008 report, some factories are forcing workers to lie about wages and conditions to outside inspectors. The group said it conducted interviews and investigations early this year in four factories making licensed bags, headgear, stationery and other products.

“It brings shame on the whole Olympics movement that such severe violations of international labor standards are taking place in Olympics-licensed factories,” said Guy Ryder, general secretary of the International Trade Union Confederation.