Apple's falling iPhone sales have had a knock-on effect on the factory workers in China who assemble the iPhone for the major Apple supplier Foxconn.

According to the South China Morning Post, workers are lining up to resign after seeing wage reductions of up to 25% and losing perks such as free laundry.

Foxconn reportedly relies on Apple for roughly a quarter of its business.

Apple's declining iPhone sales have had a knock-on effect on the poorly paid factory workers who assemble the device in China for the manufacturing firm Foxconn.

A report on Friday by the South China Morning Post sheds light on the status of workers at Foxconn's facilities in Henan province, in central China.

According to the newspaper, workers have seen wage reductions of up to 25%. That's because "peak production" — a ramp-up in iPhone production in the run-up to Christmas — didn't last as long as usual, meaning workers had fewer opportunities to add to their base salary through overtime.

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There are other signs that Foxconn has been hit by falling iPhone sales. The Post had images of seasonal workers lining up to complete their exit paperwork. It said the lines formed every day at the facility in the city of Zhengzhou.

A free shuttle service ferrying workers to the factory has also been canceled, meaning some workers have to walk 40 minutes to work. A free laundry service was also cut, meaning workers have to pay a not-insignificant chunk of their salary to do their washing and dry cleaning, the report said.

On average, the Post reported, workers at the Henan facility earn 2,000 to 3,000 yuan, or $299 to $447, a month, with the chance to earn more with overtime shifts.

One worker told the Post that 2018's peak season lasted only 20 days, versus the usual four to five months. That chopped his salary from approximately 4,000 yuan in October to 3,000 yuan in November.

"In September, our line supervisor told us that Apple added a new order for 3 million iPhone 8 Plus [units]," the worker told the Post. "It only took us about 20 days to finish the production because we worked 18 hours a day in two shifts, including weekends. The peak season didn't last long at all."

That tallies with a November report from The Wall Street Journal, which reported that Apple had cut production for its 2018 models, the iPhone XS, the iPhone XR, and the iPhone XS Max. Apple CEO Tim Cook went on to warn investors in December of weaker iPhone sales.

According to the Post, Foxconn has said it relies on Apple for 20% to 30% of its business.