The American electronics giant Apple was investigating damaging allegations last night that Chinese workers making its new iPad device were subjected to such "inhumane" treatment that some of them took their own lives by jumping off factory roofs.

Documents seen by The Independent reveal there are widespread failures by Apple's suppliers to respect standards on labour rights and safety specified by the company, which had sales of £30bn last year.

An update to the US firm's supplier codes in February revealed that a majority of its 102 facilities flouted its "rigorous" rules on working hours, which include a weekly limit of 60 hours a week – equivalent to 12 hours a day. Some 39 per cent broke rules on workplace injury prevention and 30 per cent broke guidelines on the management of toxic chemicals.

Audits uncovered violations involving child labour, falsified records and disposal of hazardous waste.

The company has been embarrassed by publicity surrounding 11 suicide attempts at the vast Foxconn facility near the southern boom city of Shenzhen, where the iPad is made, which threatens to overshadow the global launch of the touch-screen computer tomorrow.

Yesterday a "saddened and upset" Apple promised to investigate whether the plant, which employs 300,000 people who earn around 30p an hour, should continue to make its products, which sell for hundreds of pounds each.

At the 1.2-square mile Foxconn facility, which also makes products for Dell, Hewlett Packard and Acer, nine workers have died and two have been gravely injured in roof jumps in the first five months of 2010.

All the incidents involved workers aged under 25, who apparently have been disturbed by the long shifts and strict discipline. Talking and music are banned during shifts, which last at least 10 hours. Workers must perform a certain number of repetitive operations per shift, under the eye of allegedly harsh military-style supervisors.

"Foxconn's management is totally inhuman," one worker told the Reuters news agency. Another said: "They don't treat workers as humans."

A young Foxconn line supervisor, Tang Wenying, told journalists allowed into the complex yesterday: "This is a good place to work because they treat us better than many [other] Chinese factories." In an attempt to prevent more suicides, the Taiwanese-owned firm has hired 2,000 singers, dancers and gym trainers. It is also putting up netting to thwart future suicides.

Concerns were expressed about the factory three years ago by China Labour Watch, a US organisation which claims dire conditions involved "serious labour violations including excessive working hours, unpaid wages for up to 30 minutes of work each day, compulsory overtime and extremely poor dormitory conditions."

Last July, it revealed the suicide of a young worker, Sun Danyong. According to its report, only workers producing for Apple were given a stool to sit while working, while all others had to stand.

Workers also complained of violence, including beatings with iron bars and whips.

The allegations have not surprised campaigners, who say that while Western shoppers often hear of problems at Asian clothes factories, conditions for workers in cleaner, bigger consumer electronics plants are just as grim. "When you look at large-scale export-driven trade, it doesn't really matter whether the workers are making clothes or electronics," said Simon MacRae, senior campaigns officer at War on Want. "There's a similar pattern: long working hours, very poor pay and suppression of labour rights. The sector provides jobs but without decent wages you are not going to lift people out of poverty."

Last month a report by the National Labour Committee, an American NGO, found that workers at a Chinese factory supplying Microsoft, Hewlett Packard and other brands toiled for up to 15 hours a day in heat of up to 30C. Other allegations about the KYE factory included sexual harassment and humiliation by supervisors.

Teenage workers were pictured slumped over their desks during a break in a 15-hour shift. One said: "We are like prisoners. We do not have a life. Only work."

KYE management responded that conditions were excellent and fully complied with Chinese labour laws. Microsoft said it was "very concerned" and launched an investigation.

Although China has occasionally expressed concern over the regime in export factories, the spate of suicides has spurred a national debate about whether workers fulfilling foreign orders are being pushed too hard.

Campaigners believe Bangladeshi clothes factories are the very worst sweatshops, but factories in China can combine the financial advantages of a cheap labour supply with a totalitarian state's intolerance of industrial rights. Most of those in free trade export zones such as Shenzhen, the "the workshop of the world", are owned by foreign companies.

Apple, which will open its 27 stores around the UK as early as 8am tomorrow to sell the iPad, said it was taking the spate of suicides "very seriously". A spokeswoman said: "A team from Apple is independently evaluating the steps they are taking to address these tragic events and we will continue our ongoing inspections of the facilities where our products are made."

Hewlett Packard said it was investigating "the Foxconn practices that may be associated with these tragic events". Dell said it expected its suppliers "to employ the same high standards we do in our own facilities". Acer declined to comment.

Hard labour for gadgets

60 hours Maximum working week stipulated in Apple's "supplier responsibility" code of practice

54 per cent Factories breaking Apple's rules on working hours (according to Apple's Supplier Responsibility 2010 Progress Report)

39 per cent Factories breaking Apple's injury prevention rules

30 per cent Plants breaking Apple's hazardous substance rules

30 pence Hourly wage of 300,000 workers at Foxconn in Shenzhen

86F Temperature exceeded in workshops at the KYE Factory in China, which supplies Microsoft

2,000 Number of Microsoft mice mouse-makers in the KYE Factory must make per shift