Facebook has admitted that a questionnaire which asked whether it was acceptable for an adult man to ask a 14-year-old girl for indecent images was a "mistake".

"In thinking about an ideal world where you could set Facebook's policies, how would you handle the following: a private message in which an adult man asks a 14-year-old girl for sexual pictures," posed one of the survey questions, which appeared on users' home feeds over the weekend.

The multiple choice responses included: "This content should be allowed on Facebook, and I would not mind seeing it"; "This content should be allowed on Facebook but I don't want to see it"; "This content should not be allowed on Facebook and no one should be able to see it" and "I have no preference on this topic".

Guardian journalist Jonathan Haynes spotted the survey on Sunday evening, writing: "I mean, this is not the kind of topic you should be determining policy on by surveying your readers. Facebook so out of touch with the real world."