Amazon has been attacked by a labour watchdog over working conditions at a plant in China where its smart speakers and e-readers are manufactured.

The New York-based group China Labor Watch found that a factory run by Amazon’s contract manufacturer Foxconn was making staff work excessive hours on low wages.

It added that workers at the site in Hunan province had received inadequate training and said Foxconn was relying too heavily on “dispatch” or temporary employees – in violation of Chinese law.

In a 94-page report, China Labor Watch said around 40% of workers at the factory were dispatch workers, outstripping the 10% limit under Chinese law.

Dispatch workers were paid the same rate for regular and overtime hours, rather than the time-and-a-half stated by law.

The temporary staff earned 14.5 yuan (£1.69) per hour, the report said.

Workers also put in more than 100 overtime hours per month during peak season, far more than the 36 hours allowed by law. Some even worked for 14 consecutive days.

Amazon told Reuters that it audited the factory in March and found “two issues of concern”.

“We immediately requested a corrective action plan from Foxconn,” Amazon said.

The etailer added it is monitoring Foxconn’s response and “compliance with our Supplier Code of Conduct. We are committed to ensuring that these issues are resolved.”

Taiwan-based Foxconn – the world’s largest contract electronics manufacturer with more than one million employees – makes Amazon’s Echo Dot smart speaker and Kindle e-reader.

The firm, which also makes Apple’s iPhones, pledged to improve working conditions back in 2010 following a spate of suicides at its plants in China.