Facebook's photo-sharing app Moments will not be made available in Europe due to concerns about its use of facial recognition, it has been revealed, according to BBC News.

The app, which allows users to share mobile-phone photos with friends without posting them publicly, was launched in the U.S. this week.

The Irish data regulator said that users must be given a choice about whether they want it, with an opt-in.

There is currently no timetable for such a feature, said Facebook.

Richard Allen, Facebook's head of policy in Europe said: "We don't have an opt-in mechanism so it is turned off until we develop one."

Moments arranges the photos on someone's mobile phone into groups, based on when they were taken. The facial recognition technology can identify Facebook friends to whom users can then forward the photos.