Social media groups which encouraged support for UK political parties in the build up to the European elections were targets for fake news and polarising content with links to the far right, a Newsnight investigation has found.
Closed Facebook groups, whose contents can only be viewed by approved members, saw users engage with and share content linked to far-right and potentially fake accounts, including some apparently US and Russian-oriented profiles.
While disinformation was more prevalent in groups promoting the Brexit Party, it was also being shared, to a lesser extent, in pro-Remain groups. The groups were not officially associated with any party.
Posts in the groups often contained abusive language aimed at MPs.
The Brexit party told Newsnight: "We were not aware of this and we cannot spend all of our time monitoring Facebook.
"If any Facebook group is using our logo or infringing our copyright, without our permission, and is behaving suspiciously in any way, we act to close it down as we have done before and will do again."
How did we track Facebook groups?
Newsnight worked with William Dance, a linguistics and fake news expert from Lancaster University, to track disinformation campaigns. The content, history and administrators of the 30 largest and most active closed pro- and anti-Brexit Facebook groups were analysed.
The administrators of closed groups often vet new members using questions to ensure they hold views compatible with the rest of the group.
New Facebook rules, introduced after accusations the company allowed interference in elections across the world, have forced public pages to be more transparent about who runs them and who advertises on them. But as closed groups are private, they are less likely to be flagged up to Facebook moderators for rules violations.
Newsnight's investigation found that the largest group, called "Brexit Party - supporters" (it had no official link to the party) was the latest incarnation of a page setup in January 2017 under the name "Libertarians and Chartists for Trump".
It has been renamed several times to support different causes, operating as "#MBGA News >> Make Britain Great Again News" and then "South West England #FreeTommy" - a reference to former English Defence League leader Tommy Robinson - before taking on its most recent Brexit-themed name.
The group was run by a Facebook profile page called "Make Britain Great Again", containing links to the website MBGAnews.com, which in turn redirects to another site, RedPillFactory.uk.
Red Pill Factory is registered in California and has been described by critics as offering a mix of partisan and false stories on subjects including the yellow vest movement, immigration, and Brexit.
Since Newsnight contacted the site, it has removed some content, including a story claiming German authorities ordered prostitutes to have sex with migrants. There is no evidence to support that the story was true.
On Facebook, the "Make Britain Great Again" profile also shared fact-based stories from Red Pill Factory including one headlined "BANNED: Tommy Robinson Page DELETED By Facebook."
Media Bias/Fact Check, an independent website which rates the reliability of online content, describes Red Pill Factory as: "extreme bias, consistent promotion of propaganda/conspiracies, poor or no sourcing to credible information, a complete lack of transparency and/or is fake news."
In response to our investigation, a writer for Red Pill Factory said that they would "deem the notion of 'fake news' to be very subjective.
"[We] dispute claims that the site peddled fake news, but actually articles were often fact-checked," the writer said.
They added: "Persons trolling the website with fake articles or presenting inaccurate, anti-Islamic (as opposed to anti-terrorist), or racist articles were barred from submitting future articles" and said an editor was once dismissed for violating those rules. RedPillFactory has run articles heavily critical of the yellow vests movement as of late - one contributor was sacked for promoting yellow vests."
"Brexit Party - supporters" was shut down before the European elections, after a Sunday Times investigation into its administrators.
In response to the Sunday Times story, The Brexit Party said it would formally approach Facebook to demand that the groups were taken down: "We have no interest in these people at all, absolutely not."
Possible foreign influence?
Meanwhile, other closed groups continued to spread links to disinformation.
"We Support Brexit" closed group, which has around 3,900 members, included a number of posts from a user who appears to be Russian. The user repeatedly shared links from News Front, a website that the EU's anti-disinformation East Stratcom Task Force has identified as a source of pro-Kremlin fake news.
The picture associated with the user's profile appears to be of a former Russian Miss World and in all likelihood does not show the person behind the account. The profile is entirely in Russian, and the cover photo features Vladimir Putin.
Newsnight attempted to contact the user, but they did not respond.
The user account and the News Front site formed part of a wider pattern of disinformation or polarising content with foreign links being shared in pro-Brexit closed Facebook groups, which was then shared and engaged with by other users.
This includes content from Infowars, a conspiracy site, and NewsPunch, which was previously known as YourNewsWire, a site which was also criticised by the EU's East Stratcom Task Force for "publishing fake media stories that support Russia's policies."
NewsPunch editor Sean Adl-Tabatabai told Newsnight: "We are a news organization that publishes information from a variety of different sources on a wide variety of subjects. Sometimes this includes the BBC itself. To call us 'fake news' is libellous and damaging to our reputation.
"We have no control over members of the public who choose to share our content on any platform, including Facebook. At the moment, it is still their prerogative to freely read and share things as long as they are not breaking the law."
The BBC has also tried to contact the people who run News Front, but has not received a response.
Posts from a website called Brexit Betrayal News were also shared across a number of closed groups by a Facebook user who appears to be in the US.
Mr Dance estimates that the posts targeted 50,000 people who belong to groups such as "Brexit the Protest" and "We Are The 17.4 Million".
As well as listing Brexit Party MEPs, the site shared links to the QAnon conspiracy which was popularised by fringe and alt-right groups in the US.
The Brexit Betrayal News domain was registered in Chicago in April 2019. When contacted through the site, the user confirmed that the website was hosted in the US, but refused to confirm whether they are from the US.
What about pro-Remain groups?
Disinformation appeared less prevalent in the pro-Remain closed groups Newsnight analysed. Last year, groups with names such as "Say NO to "Brexit"!" and "Labour Against Brexit" occasionally included links to polarising news stories, some of which came from sites hosting false stories.
In other large closed groups, including "Remain Together" and "UK Citizens - Say Yes 2 Europe - Remain in the EU", links led almost exclusively to mainstream news networks.
Why does it matter?
In April, the Mueller report on potential interference in the 2016 US elections flagged Facebook groups as a breeding ground for foreign interference. According to the report, as early as 2014 Russian users were setting up small Facebook groups designed to attract US audiences and look as if they were controlled by American activists.
Mr Dance explained: "These groups may be set up and operated with honest intentions but then fall victim to people intentionally sharing disinformation and misleading news.
"Facebook groups can be manipulated to foment political resentment and to stoke social tensions. In the age of social media, it is simple and low-cost to reach tens of thousands of people with biased and false news," he said.
Disinformation is not the only type of controversial content identified by Newsnight's investigation. Abuse "aimed at politicians from all parties" was also prevalent, said Mr Dance.
The "Brexit Party Supporters group" (a different group to the one which was shut down) has more than 6,000 members and included language such as "HANG THEM HIGH" referring to Change UK candidates.
Extremely offensive language was also directed at former prime minister and Remain campaigner Gordon Brown and shadow home secretary Diane Abbott.
In pro-Remain groups, similar language could be found, albeit less frequently. In "No To Brexit!" one user referred to Brexit Party MEP Ann Widdecombe, saying: "Hanging is too good for Quitlings". Another user, referring to Theresa May, wrote: "she is barking mad and needs putting down".
Facebook told Newsnight it could not comment on individual groups.
In a statement, the company said: "In the run-up to the European elections we made major investments to help protect the integrity of the elections and prevent abuse of our platform.
"Across the EU, we have removed a number of fake and duplicate accounts that were violating our authenticity policies, as well as pages for name change and other violations. We also have a continuous programme that identifies and removes coordinated inauthentic behaviour by anyone across our platform."
What did the closed group administrators say?
Newsnight asked for comment from the administrators of the various groups which hosted posts spreading disinformation and abusive language.
One administrator of "Labour Against Brexit" said: "We regularly remove posts which do not fall within our guidelines (and often the posters with them). We have very occasionally identified individuals who seem to be infiltrators or trolls, and removed them. And our members are quite assiduous in reporting dodgy content."
An administrator of "Brexit The Protest" said that the group "moderates everything" and that he had "not seen any disinformation being shared on the group."
And an administrator for "We are the 17.4 Million" said: "We are a small team of volunteer administrators. All initial posts must be approved by admins. At this stage we regularly weed out extremism, hate speech and profanity and ban people from the group.
"We lack the resources to police proactively comments underneath posts but do take action when a member reports something unsavoury."
Reporting by Marianna Spring and text by Lucy Webster
Have a story for us? Email BBC Trending