Apple retorted to environmental campaign group Greenpeace's claims calling it the 'dirtiest' of the technology giants for the second successive year due to the way it powers its cloud-based services.
Greenpeace, in its annual report on Internet firms, said that Apple relied on coal power for services such as iCloud and the voice-controlled "personal assistant", Siri, more than its rivals like Facebook and Google.
"Apple right now is falling behind companies like Google and Facebook, who are taking a leadership role on this issue," The Telegraph quoted Greenpeace spokesman Dave Pomerantz, as saying.
"It's a shame that a company that built its reputation on thinking differently is now behind the curve," Pomerantz added.
Apple, however, responded before the report was published on Tuesday, highlighting the green credentials of its enormous billion-dollar data centre in Maiden, North Carolina, and a second it plans to build in Oregon.
Greenpeace claimed that the North Carolina facility, which opened last year to support the launch of iCloud, Apple's suite of online backup services, would need up to 100MW in power and that renewable energy would meet for only ten per cent of demand.
Apple, however, responded that the data centre would in fact consume a peak of only 20MW, of which 60 per cent would come from renewable sources such as a 171-acre solar array it is building nearby.
Greenpece's report, which praised Google and Facebook for their heavy investments in renewable energy, accused Apple of being highly reluctant to disclose anything about their data centre operations.