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.

Facebook supports delay of embattled Libra project, Zuckerberg to tell Congress Read more

Until August, Facebook’s third-party fact checkers, all of whom are independent organisations and members of Poynter’s International Fact-Checking Network, were appointed by the company to only vet content posted to social network by users. The companies receive a fee for the work, and use tools built by Facebook to find claims posted to the site and mark them as true or false. Other flags, including satire, false headline, and “mixture”, are also available.

But a policy update published late this summer allowed fact checkers to flag false adverts for the first time. The new policy was introduced quietly by the company, and initially noticed for the effect it had on political adverts: fact checkers are not allowed to vet content posted by political candidates, and so those adverts can never be taken down for misinformation.

But the ability to vet adverts at all is a new feature for fact checkers, and one some of them are not entirely comfortable with. When a user post is marked false by a fact checker, it gets flagged as such on the site, and shared to fewer users as a result, but it does not get removed from view entirely – a conscious decision on the part of Facebook and fact checkers, who do not want to be accused of censorship.

But Facebook’s policy about non-political advertising is sharper: the company prohibits adverts marked false. “We disapprove ads that contain content rated false, which means these ads can’t run,” Facebook says in a help document, updated in early September according to the Internet Archive.

“Several of us really don’t want that power,” one fact checker told the Guardian. “One of my first questions is, why are you now giving us powers to remove content when you haven’t before? I would argue you’re opening up yourselves to liability. That’s just a Pandora’s box in my opinion.”

Quick guide What is Libra, Facebook's proposed cryptocurrency? Show Hide What is Libra? Facebook says Libra is a 'global currency and financial infrastructure' - a digital asset built by Facebook and powered by a new Facebook-created version of blockchain, the encrypted technology used by bitcoin and other cryptocurrencies. The name Libra comes from the basic Roman measurement of weight. The abbreviation lb for pound is derived from Libra, and the £ symbol originally comes from an ornate L in Libra. Why is Facebook launching a cryptocurrency? Facebook claims it wants to reach the 1.7 billion people around the world who do not have access to a bank account. Who is in charge of Libra? Facebook is likely to run into regulatory hurdles and antitrust concerns. The currency will be serviced by a collective of companies called the 'Libra Association'. It functions as what is known as a 'stablecoin', pegged to existing assets like the dollar or euro, in the aim of making it less subject to the volatility that many cryptocurrencies experience. The Libra Association is described by Facebook as an independent, not-for-profit organisation based in Switzerland. Within the Libra Association will be a governing body called the Libra Association Council, comprised of a representative of each member of the association, which will vote on policy and operating decisions. Facebook claims that although it created the Libra Association and the Libra Blockchain, once the currency is launched in 2020 the company will withdraw from a leadership role and all members of the association will have equal votes in governance of Libra. The companies who contributed a minimum of $10m(£8m) to be listed as founding members of the Libra Association include tech companies such as PayPal, Ebay, Spotify, Uber and Lyft, as well as financial and venture capital firms such as Andreessen Horowitz, Thrive Capital, Visa and Mastercard. However in October 2019 several of the companies that had been backing the initiative announced that they were pulling out, including Visa, Mastercard, PayPal and Stripe. How and when can I use it? With regulators asking questions and backing companies dropping out, it is unclear now if Libra is still viable. Facebook's original plans were that users could download Calibra, a digital wallet, that would allow them to send the currency to anyone with a smartphone. It is no longer clear which countries the coin will launch in first, if at all, though Facebook had said 'almost anybody' in the world with a smartphone would be able to download the app. Kari Paul in San Francisco Photograph: Chesnot/Getty Images Europe

Facebook has started to roll out the new ad-checking features to US fact checkers, and the company says it will communicate with international fact checkers before it launches overseas.

As a result of the lack of communication, some fact checkers only learned that their responsibilities were shortly about to change due to media reports of the new policy around political adverts. Others found out watching Zuckerberg in front of Congress, when Congresswoman Maxine Waters asked him: “Do you fact check on any ads at all?”, and he answered “Yes”.

“They added language to the guide without telling us,” another fact checker said. “We had to check previous versions to find out when.”

Facebook declined to comment. Full Fact and FactCheckNI, the two British partners for Facebook’s fact-checking service, declined to comment.