Apple has launched a delicately worded attack on Google and Facebook over their invasive business practices, with CEO Tim Cook claiming that Apple doesn't "read your email or your messages".

In an open letter, Apple outlined its privacy model, comparing it favourably to that of their competitors who sell user data to advertisers.

It said: "A few years ago, users of Internet services began to realise that when an online service is free, you're not the customer. You're the product. But at Apple, we believe a great customer experience shouldn't come at the expense of your privacy."

"Our business model is very straightforward: We sell great products. We don't build a profile based on your email content or web browsing habits to sell to advertisers.

"We don't "monetise" the information you store on your iPhone or in iCloud. And we don't read your email or your messages to get information to market to you."

These are not very veiled criticisms of Google and Facebook, companies that store their users' data for targeted advertising.

Google is being investigated in Europe by privacy commissioners over changes it made to its privacy policy in 2012. Meanwhile, Facebook is under fire for both its Facebook Messenger app and the psychological experiment it conducted on unknowing users earlier this year.

In this out-of-the-ordinary privacy statement, Apple also clarified how its own advertising model works.

"One very small part of our business does serve advertisers, and that's iAd. We built an advertising network because some app developers depend on that business model, and we want to support them as well as a free iTunes Radio service.

"iAd sticks to the same privacy policy that applies to every other Apple product. It doesn't get data from Health and HomeKit, Maps, Siri, iMessage, your call history, or any iCloud service like Contacts or Mail, and you can always just opt out altogether."

Apple itself has recently been at the centre of a privacy scandal, as nude photos of celebrities such as Jennifer Lawrence were stolen from its iCloud and leaked all over the internet.

Tim Cook went on to address the last year's NSA scandal in which it was revealed that US intelligence services had accessed digital data from companies including Apple.

"I want to be absolutely clear that we have never worked with any government agency from any country to create a backdoor in any of our products or services. We have also never allowed access to our servers. And we never will."