The National Labor Committee (NLC) has found what it calls "illegal and sweatshop conditions" at a Chinese factory supplying HP, IBM, Intel, Cisco and Jabil.
The Jabil Circuit factory in Guangzhou, China, employs 6,000 workers and makes products for multinational technology firms, all of whom are members of the Electronic Industry Citizenship Coalition (EICC), which aims to promote sustainable and ethical working practices in the technology industry.
The factory is not the first technology supplier that has been found with poor working conditions, and technology firms have said in the past that they are working to address the issue.
The NLC says conditions at the factory are "cruel and inhuman" and that it operates like a minimum security prison.
The factory operates 24 hours a day, seven days week, with workers standing for the entire duration of their 12-hour shift. They report stiffness and soreness in their necks, shoulders, arms and legs, and say their feet swell up.
They are allowed only one bathroom break in eight hours and security guards patrol the factory floor while they are working.
The NLC report says, "Workers who make a mistake are forced to write a 'letter of repentance' begging forgiveness - which they must read aloud in front of all their co-workers. They can also be made to stay after work - unpaid - to clean the toilets."
Six workers share small dormitory rooms where they sleep in bunk beds, and are paid 93 cents an hour.
NLC director Charles Kernaghan said, "US companies bought into the 'China model' of exploitation, pitifully low wages, gruelling hours, miserable living conditions and zero rights.
"Corporate monitoring never works. Five out of eight of the companies on the board of the EICC have been producing their goods for years under illegal, harsh, sweatshop conditions at the Jabil factory."
A spokesperson for Jabil Circuit said the company was reviewing the allegations. "This lengthy summary paints a very accusatory, but not very accurate, picture. Jabil takes employee working conditions and rights very seriously and we are vigilant about conducting employee surveys to be sure we are proactively addressing any issues."
HP said, "We take allegations such as this very seriously. We are investigating the matter and will take all appropriate actions once the investigation process is complete."
The other companies named in the report declined to comment.