Celebrity iCloud accounts were broken into by hackers who correctly answered security questions or subjected victims to phishing attacks, according to Apple’s chief executive Tim Cook.

The company denies that a complacent attitude on its part led to the leaking of naked celebrity pictures this week, adding that credentials were not taken from its servers.

Cook told the Wall Street Journal: "When I step back from this terrible scenario that happened and say what more could we have done, I think about the awareness piece.

"I think we have a responsibility to ratchet that up. That’s not really an engineering thing."

Apple has been criticised in recent weeks for alleged flaws in its Find My iPhone feature that may have been abused to allows hackers access to celebrity iCloud accounts.

The firm has said it update its security features in the wake of the attack, with iCloud customers soon to be sent alerts when new devices are used to access their accounts or restore data.

Apple will also more actively promote the use of two-factor authentication on its mobile operating system iOS, requiring users to have several codes, some generated for one time use and some issued when a user registers for its services.