Facebook fact checkers did not know they could vet adverts

Many third-party contractors learned of new policy from Mark Zuckerberg's testimony to Congress

Many of Facebook's third-party fact checkers have still not been told that the company now expects them to vet adverts as well as user content for misinformation - though, controversially, not political adverts.

Some fact checkers only found out that they should be vetting paid adverts after Facebook chief executive Mark Zuckerberg described the new policyin Congress on Wednesday.