Social media companies should be prosecuted like publishers if they fail to remove abuse content, an influential committee is to tell the Government.
Social media companies are not currently regulated as publishers but are instead considered as platforms as they have limited control over the content they host.
This means that racist, extremist and child abuse content on Facebook, Google or Twitter does not receive the same sanctions as if it were published by a news organisation.
In a report being presented to Theresa May tomorrow, the Committee on Standards in Public Life will call for a change of the law to allow social media companies to be prosecuted like publishers, according to The Times.
The committee, which advises the Prime Minister, has recently investigated the intimidation of Parliamentary candidates and received evidence relating to June's General Election from Facebook, Google and Twitter.
Jim Killock, executive director of Open Rights Group, described the call to censure web giants as "an attempt to make Mark Zuckerberg a national censor".
He said: "Facebook and Twitter will censor legal material because they are scared of fines.
"They are the worst people to judge right and wrong. Theresa May is in danger of removing people's right to a proper legal decision."
The committee's call comes months after the Conservatives made a manifesto pledge for a Digital Charter, which may include a move to tax social media sites to pay for action to tackle online bullying.
Confirmed in the Queen's Speech, the Digital Charter has ignited concerns from digital rights groups about the possible implications for civil liberties.
In the manifesto, the party said it would also introduce sanctions for companies that fail to meet their legal duties over content that is considered to be a breach of law.
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The difficulties in establishing whether content could be illegal or not were highlighted earlier this year when YouTube deleted an archive of video evidence of potential war crimes in Syria.
In 2012, Twitter user Paul Chambers had his conviction overturned in the High Court after a joke threat on the messaging platform: "Crap! Robin Hood airport is closed. You've got a week and a bit to get your s*** together, otherwise I'm blowing the airport sky high!"