To Western children, Disney is a fairytale world of talking mice, princesses and dragons. To Chinese children, it sometimes means working from 8am to 10pm, handling chemicals without protection, being chastised for failing to hit production targets, and eating food laden with cockroaches.

Staff at two factories making Disney toys for Westerners employed children between the ages of 14 and 16 in breach of local labour laws and the entertainment giant's own code of conduct, according to a report by China Labour Watch (CLW), a US NGO.

Along with their adult colleagues, the children worked 12-hour days in "unacceptable conditions", the 25-page document says. One factory was making Winnie the Pooh and Piglet toys and the other was making Disney dolls and stamps. They also made goods for other companies.

CLW said it launched the undercover investigation because problems had been found at factories producing Disney-branded goods in the past. In 1996, another NGO, the US National Labour Committee, found abuses at suppliers in Haiti in a report called The US in Haiti: How to get Rich on 11c an Hour.

Last year, CLW found breaches of working hours, wage and contract laws at a factory in Guangdong that was producing Disney gifts after a 17-year-old worker, Liu Pan, was crushed to death in machinery. CLW claimed the factory was hiring workers as young as 13. To uncover current conditions, CLW randomly selected two plants making Disney-branded merchandise, sent in undercover investigators and interviewed staff.

According to the report, working hours were excessively long: two four-hour stints daily between Monday and Saturday were typically followed by another four hours of compulsory overtime in the evenings, adding up to 76 hours a week. The children also worked these hours, up to 330 a month, including 150 of forced overtime, it said, adding they sometimes worked seven days in a row.

Workers were supplied with gloves for handling hazardous chemicals but allegedly did not wear them because it made their work rate too slow. As a result, some of them had developed skin rashes, while for some, layers of skin were "falling off".

Staff complained they found it difficult to resign, and could do so only at set times, leaving with less pay than they were owed. There were "harsh and unreasonable" discipline practices, and dormitories – housing typically 12 workers each – were said to be dirty and smelly. Daily food at one of the factories consisted of two vegetable dishes and one meat meal. The report said: "In all of the meat dishes, one can only see two small pieces of meat or fish. Regardless of what kind of food or oil it is cooked in, workers often detect food additives, hair or cockroaches."

Although members of staff were allowed to join a trade union, they were not aware it existed and were not members. There was no safety training, no fire drills and "fire hazards existed", the report said. After deductions for accommodation, meals and drinking water, one factory paid 1,100 yuan (£103) a month – about three yuan an hour.

CLW said: "The investigations showed the old problems with Disney remain: child labourers are still hired in factories, and labour conditions are still unacceptable." It called on Disney to publish details of its supplying factories and open them up for some independent inspections.

Disney said it had sent investigators into the factories this week. A spokeswoman said: "Clearly the conditions outlined in this report are a breach of our labour standards and are unacceptable. We have started to investigate. As far as we can see, one of the factories is not authorised to make Disney products and the other is authorised to make Disney products on another site. For the most part we don't have direct relationships with the factories. The factories undertake multiple relationships with our licensees. We work very hard to ensure that factories are monitored on a regular basis."