The report also claimed that measures reportedly designed to address workers' grievances - including large pay rises and mental health services - deceived the public; workers complained they did not benefit from the new measures.

In a joint open letter, researchers from the 20 universities urged Terry Gou - chairman of Foxconn's Taiwanese parent company, Hon Hai Precision Industry - to respect workers' legal rights and fulfil the company's social responsibilities.

'Terry Gou publicly blamed personal problems for the suicide attempts and the media reported that Foxconn planned to expand its workforce to 1.5 million people across the mainland. We worried about what a fast-expanding enterprise, without thorough introspection about the suicide tragedies, would bring to its workers,' the letter said.

The researchers reported that employees were forced to work 80 to 100 hours of overtime per month. Under China's labour law, the legal limit on overtime is 36 hours a month.

Tens of thousands of teenage vocational school students, many without the protection of labour contracts or statutory industrial insurance, work under the same conditions in Foxconn's factories.

Burson-Marsteller, a public-relations firm representing Foxconn, said in a statement that Foxconn was committed to providing a safe and positive working environment, and that it respected all laws and government regulations. The statement admitted that Foxconn provided training to teenage vocational students, but denied that they worked without statutory protection.

The report said supervisors sometimes forced employees to work overtime without pay, after Foxconn announced it would not pay for overtime work exceeding 80 hours per month. This measure was to discourage extensive overtime working, the company said.

Workers complained to the researchers that the assembly lines ran too fast, and that they were required to finish every procedure in exactly two seconds. 'Workers aren't allowed to talk, smile, sit down, walk around or move unnecessarily during their long working hours, which require them to finish 20,000 products every day,' the report said.

About 13 per cent of those interviewed said they had passed out on the assembly line because of the high pressure and long hours. Twenty-four per cent of female workers complained they had suffered menstrual disorders due to excessive work.

The researchers found that most workers did not benefit from the large-scale pay rise promised by Foxconn. Many interviewees said their quarterly and annual allowances had been cancelled and work pressures were increased.

The report said what it called Foxconn's inhumane management style abused workers mentally and physically. 'In our survey, nearly 28 per cent of workers had been verbally insulted by their supervisors or security guards, 16 per cent had suffered physical punishment and 38 per cent said their personal freedom had at least once been illegally restricted.'

One Foxconn worker said: 'Although the salary here is better than at many other sweatshops where I worked before, you can never find someone to air your grievances with because everyone is isolated here, and you'll gradually become insane.'

The report found that a consultation centre - supposedly meant to identify workers who are feeling suicidal - actually violates workers' privacy by trying to pressure workers into informing on each other.

Endless toil

The legal limit on overtime in China is 36 hours per month

According to the report, Foxconn workers have put in overtime, in hours per month, of up to: 100