Facebook users are being warned that the popular social networking site accidentally exposed personal information about its members this week.

Sophos has warned that Facebook users that the social networking site has accidentally revealed personal information about its members during the public beta tests of its new profile design for members.

According to Sophos, earlier this week, the full dates of birth of many of Facebook's 80 million active users were visible to others, even if the member had requested the information remain private.

The exposed user profiles could be useful to identity thieves and can be a golden nugget for a committed identity thief, warned Graham Cluley, senior technology consultant at Sophos.

Sophos claimed it notified Facebook’s administrators and the error appears to be resolved but is advising users to use a fake birth date in future as a precaution.

"It's good that Facebook fixed the problem - but can people feel confident that this kind of mistake won't happen again in future?" said Cluley.

He added: "My advice to Facebook users would be, even if your date of birth is set to be non-visible, change it to a made-up date in case this kind of blunder happens again. Facebook and other social networking websites need to be more careful about protecting their members' data, or risk losing users."

New user profiles can be accessed via www.new.facebook.com. According to the Facebook developer’s blog, Facebook will start rolling out the new profile page design to users this week.