NSA whistleblower Edward Snowden has issued a chilling warning about Apple's plans to begin scanning iPhone photos of users, saying the proposal will give governments terrifying access to citizen's private data.

Snowden, a former computer intelligence consultant, who in 2013 leaked classified documents to show the scale of government snooping on U.S. citizens, condemned the new plans in strong terms, and says they set a precedent which will ultimately be abused by corrupt politicians to destroy individual privacy.  

He said that Apple had chosen a dangerous path with their scheme to access users' photos, and that governments will manipulate the rule to give them greater access to data they claim they need access to - such as a phone owner's presence at a protest. 

The Silicon Valley giant will scan all photos linked from iPhones to the Cloud for child pornography - with images cross-checked against a database from the National Center for Missing and Exploited Children.

Apple say that any users who do not want their phones to be scanned can switch off the linkage to the Cloud. But many people do not realize their phones are synching with the Cloud - and Snowden said 85 per cent of iPhone users have their phones set up to synch to the Cloud.

He also warned that Apple's initial opt-out will inevitably be axed if its plans go ahead, meaning people's phones will ultimately be the property of corporations and governments, and used to spy on their owners.  

The update was announced at the beginning of this month, and Apple said the latest changes will roll out this year as part of updates to its operating software for iPhones, Macs and Apple Watches.