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.
"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."