SACOM was due to deliver its new report on Friday to Apple and Lens Technology, based in the southern Chinese province of Hunan.
SACOM spokeswoman Liang Pui-kwan said the group was not only targeting Apple.
Working with vocational training companies, the factories bring in students to supplement their workforce, which SACOM said deprives them of their "right to a quality education.
According to the report, SACOM said that factory conditions are also hazardous.
The overall salaries of Foxconn workers dropped even though basic pay has increased, as overtime work has been cut, SACOM found.
The welfare of our employees is without a doubt our top priority and we are working hard to give our more than one million employees in China a safe and positive working environment," Foxconn Technology Group said in an emailed statement after Reuters forwarded them the SACOM report.
According to SACOM
, construction and production take place side by side, leaving the workers exposed to numerous hazards including dust residue and dangerous materials.
report highlighted excessive overtime, meager wages and poor worker safety in the two factories.
said many Foxconn employees worked 80 to 100 hours of overtime a month, on top of their regular 174 hours, which the report said was more than three times China's legal limit.
, which published the study to coincide with Foxconn's annual general meeting in Hong Kong this week, revealed that the workers are even forbidden from using electrical gadgets such as kettles or laptops.