Facebook is opening up a war room to quickly respond to election hoaxes.
Twitter is banning political ads. Google plans to crack down on bogus videos on YouTube.
Social media platforms say they are mounting a vigorous campaign against misinformation in the lead up to next month's general election in the United Kingdom.
But digital misinformation experts believe British voters remain vulnerable to the same type of misleading ads and phony claims that played a role in the vote to leave the European Union three years ago.
Government inaction on online misinformation and digital ad regulations have added to the pressure internet companies are under as they face growing criticism for amplifying false claims during the run up to the 2016 Brexit referendum and the 2016 election in the US.
Prime Minister Boris Johnson pushed for the snap December 12 election, in which voters will choose their representatives in Parliament, hoping his Conservative Party will gain enough seats to break a stalemate over his plan to take Britain out of the EU.
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And with campaigns barely under way, falsehoods are already spreading online.
A video posted this week on Twitter and Facebook by the Conservative Party contains a misleading edit of a television interview with a senior Labour Party figure.
The video had been altered to show the official failing to answer a question about Brexit, when, in fact, he responded quickly.
The chairman of the Conservative Party called the doctored video lighthearted satire, but it's part of a serious problem confronting British voters, according to Will Moy, chief executive at Full Fact, an independent, London-based fact-checking organization.
"The biggest risk to people in the UK right now is being lied to by their own politicians," said Moy, whose organisation works with Facebook and others as a third-party fact checker, as does The Associated Press.
He said laws written decades ago to cover political advertising for print, radio and television can't be applied to the reach and speed of the internet.
Public debate surrounding the 2016 Brexit vote was driven in part by a number of false claims.
They included promises that Britain could recoup 350 million pounds per week by leaving the EU an unfounded claim that a survey later found was believed by nearly half of all Britons.
The threat has grown alongside the influence of social media and the proliferation of online political ads.
The proportion of campaign spending on digital advertising has increased from 0.3 per cent in 2011 to 42.8 per cent in 2017, according to the UK's Electoral Commission.
The 2016 US presidential election and the Brexit referendum also highlighted concerns about online foreign interference, after allegations that Russia tried to use social media to divide Americans on hot-button topics like race and religion.
A similar tactic may have been used ahead of the Brexit vote: A 2017 study by the University of California Berkeley and Swansea University in Wales found more than 150,000 Twitter accounts with ties to the Kremlin that dispersed messages both supportive and critical of Brexit.
Russia has repeatedly denied meddling in the election.
Fallout from the US election also showed that online advertisers can mine data collected from social media accounts to target ads to specific audiences.
London-based political consultant Cambridge Analytica collected data from millions of Facebook accounts without the users' knowledge to profile voters and help US President Donald Trump's election campaign.
Despite reports urging new regulations designed to combat misinformation or regulate the way digital ads are targeted at voters, officials in Britain have made no significant changes to laws governing online ads, social media and election disinformation.
That's left private, giant tech firms such as Facebook, Twitter and Google to decide how best to police such content through a patchwork of policies.
The UK election will be among the first since the start of Twitter's new policy prohibiting paid political advertisements, which takes effect November 22.
The move was hailed by some as an important step in reducing election misinformation, though critics said it was overly broad and questioned its significance, given Twitter's relatively modest number of political ads.
"We believe political message reach should be earned and not bought," Twitter CEO Jack Dorsey tweeted.
Twitter's ban stands in stark contrast to Facebook's policy of not fact checking ads from politicians and allowing demonstrably false ads to remain up.
This week a group of 10 UK-based technology researchers, transparency advocates and non-profit tech organisations called on Facebook and Google, which operates YouTube, to follow Twitter's lead.
Despite the criticism, Facebook's leaders insist they understand the stakes and take the threat of misinformation seriously.
"We have learned the lessons of 2016, when Russia used Facebook to spread division and misinformation in the US presidential election," Richard Allan, Facebook's vice president of policy solutions, wrote in a piece published last month in The Telegraph.