Facebook members have been warned about a scam which purports to offer them a ‘‘dislike’’ button to condemn their friends’ posts.

The social networking website said it was investigating examples of the hoax which tricks members into giving away permission to access their profile pages.

The scam was launched amid calls for the introduction of an official dislike feature to accompany the ‘‘like’’ button already in place, according to IT security firm Sophos.

Two versions of the scam, which tempts users by appearing to come from a friend, were reported to Facebook by Sophos.

When users click on the link it prompts them to install a rogue application, which does not function as a dislike button.

Once a user has given it permission to access their profile, it updates the user’s page with a link and a message: “I just got the dislike button, so now I can dislike all of your dumb posts lol!!!”

Graham Cluley, of Sophos, said: ‘‘Facebook users should think carefully before they click on an unknown link in a friend’s status update as these scams are becoming increasingly common.

’’Giving away personal information in a survey and allowing an application access to your profile is extremely risky and Facebook users need to wise up to this rather than just clicking on links that they see, just because they appear to be from a trusted source.’’