Facebook has attempted to downplay privacy concerns after the company quietly switched on technology that automatically identifies people in photographs.
The face recognition technology is now available to users around the world, the feature picks out friends from newly-uploaded photographs and recommends suitable name tags.
The Tag Suggestions function has been switched on by default for the majority of its users.
The company has attracted criticism as it made no announcement about the change that members have to opt out of through their personal settings.
"Yet again, it feels like Facebook is eroding the online privacy of its users by stealth," said Graham Cluley, of the British internet security firm Sophos.
"Many people feel distinctly uncomfortable about a site like Facebook learning what they look like, and using that information without their permission."
Following the criticisms of the company roll-out, Facebook said "we should have been more clear with people during the roll-out process when this became available to them".
It added that the facial recognition technology would only be applied to newly-uploaded photos.
How to disable the feature
Users can disable Tag Suggestions by turning off the "suggest photos of me to friends" option on their Privacy Settings page. Mashable has posted a guide to disable the feature:
I. Go to your privacy settings.
II. Click "Customize settings."
III. Scroll down to "Things others share."
IV. Find "Suggest photos of me to friends."
V. Edit accordingly.