Facebook admits that 83m of its accounts are fake

"Advertisers will not continue to do business with us, or they will reduce the prices they are willing to pay to advertise with us, if we do not deliver ads and other commercial content in an effective manner, or if they do not believe that their investment in advertising with us will generate a competitive return relative to other alternatives."

An investigation by the BBC last month revealed that companies are wasting large sums of money on adverts to gain "likes" from Facebook members who have no real interest in their products.

It also found that some accounts are run by computer software with one person controlling thousands of profiles from a single desk, handing out commands such as: 'like' as many pages as you can to create a large community.

"Companies who are considering advertising on the social network want to be sure that any 'likes' they receive are from genuine users, not bogus accounts," said Graham Cluley, senior technology consultant at Sophos, in a blog post.

"Of course, it's far from simple for Facebook to determine reliably if every account is fake or not, as anybody can create an account with a bare minimum of credentials.