Apple CEO Tim Cook has responded to an investigative report that revealed labor abuses at one of the company's Chinese suppliers, saying he's "deeply offended" by the allegations. In an internal email to UK employees obtained by the Telegraph, Jeff Williams, Apple senior vice president of operations, wrote that both he and Cook are "deeply offended by the suggestion that Apple would break a promise to the workers in our supply chain or mislead our customers in any way."

The email was in response to a BBC documentary released this week, in which undercover journalists working at a Pegatron factory in Shanghai reported that workers there were subjected to long hours without breaks, and under cramped living conditions. In the email, Williams said that the hour-long documentary "implied that Apple isn’t improving working conditions. Let me tell you, nothing could be further from the truth." He went on to say that the company provided the BBC with "facts and perspective" on its efforts to improve working conditions throughout its supply chain, but that input was "clearly missing from their programme."

"Let me tell you, nothing could be further from the truth."

The plant in question manufactures iPads and iPhones for Apple, which employs around 1,400 workers across China. The BBC reported that employees there were forced to work shifts that lasted up to 16 hours, and that some worked 18 days in a row after their requests for time off were denied. One reporter was made to share a small dorm with 11 other workers.

Apple and other technology companies have come under increased scrutiny in recent years for alleged labor abuses in their supply chains, most notoriously at plants owned by Foxconn. Last year, a labor rights watchdog accused Pegatron of committing safety and environmental violations at its factories, in addition to labor abuse allegations that are similar to what the BBC reported this week.

In response, Apple has increased efforts to monitor and regulate its supply chain, as detailed in its annual supplier responsibility reports. In the internal email, Williams noted that the company has tracked the working hours of more than 1 million supply chain workers, and that 93 percent comply with the mandated 60-hour working week limit, though he acknowledged that there's room for improvement. "We can still do better. And we will," he wrote.

"We can still do better. And we will."

The BBC investigation also reported that tin from an illegal mine in Indonesia may be making its way into Apple's supply chain, with some of the mines employing child laborers under unsafe working conditions. In the email, Williams contests that Apple has publicly acknowledged that "tin from Indonesia ends up in our products, and some of that tin likely comes from illegal mines," and that the company has visited the region and is "appalled by what's going on there." He added that Apple is actively working to hold tin suppliers accountable, after having created an Indonesian Tin Working Group with other tech companies.

"Apple has two choices: We could make sure all of our suppliers buy tin from smelters outside of Indonesia, which would probably be the easiest thing for us to do and would certainly shield us from criticism," Williams wrote. "But it would be the lazy and cowardly path, because it would do nothing to improve the situation for Indonesian workers or the environment since Apple consumes a tiny fraction of the tin mined there. We chose the second path, which is to stay engaged and try to drive a collective solution."

Williams' full email is below.