Social media sites are "a cesspit" and systems to monitor offensive content are not working, an MP has claimed.
At a hearing of the Home Affairs Select Committee, Stephen Doughty questioned representatives of YouTube, Facebook and Twitter about extreme right-wing content that can be found "in seconds".
Mr Doughty said: "Your systems are simply not working and, quite frankly, it's a cesspit. It feels like your companies really don't give a damn.
"You give a lot of words, you give a lot of rhetoric, you don't actually take action."
Mr Doughty added he had managed to find footage of the March terrorist attack in New Zealand in seconds.
The Labour MP told the trio: "You're all three of you not doing your jobs."
Neil Potts, from Facebook, stressed that the network has 2.7 billion users and said it does "an extremely good job" in taking material down.
Katy Minshall, representing Twitter, said safety is the company's "top priority" and it will continue to invest in tools that identify users who break rules.
YouTube's Marco Pancini said the company is working with non-governmental organisations in 27 European countries to improve detection of offensive content.
The committee heard that supporters of the New Zealand attacker had deliberately uploaded altered versions of the footage to avoid detection by the systems designed to identify offensive and illegal content.
Mr Pancini said that, of the 8.7 million pieces of content taken down from YouTube in the last quarter of last year, 71 per cent were flagged by machine, and, of those, 73 per cent were removed with no views.
SNP MP Stuart McDonald said algorithms used by the site led to innocent users searching for politics, news and football being directed towards right-wing content.
Committee chairwoman Yvette Cooper highlighted a closed Facebook group with 30,000 members, in which some users have said that she and her family should be shot.
"It describes itself as a direct action group. It makes a reference to me and my family and says 'Just shoot them, criminals'.
"There's another reference to somebody else saying they should be shot, and somebody else saying 'Kill them all, every f****** one, military coup, national socialism year one, I don't care as long as they are eradicated'."
She accused Facebook of providing "safe places to hide for individuals and organisations who spread hate".
Mr Potts said action would be taken to remove the users and with police if necessary.