But as footage of the attack continued to be uploaded across the platforms, Tom Watson, deputy leader of the Labour party, criticised the tech companies' response.

"Failing to take these videos down immediately and prevent others being uploaded is a failure of decency," he said in a statement to BuzzFeed News. "I will be writing to social media companies to ask how, in this hour of international tragedy, they failed the victims of this attack and all platform users so lamentably.

"I will also be speaking to my Conservative counterparts in government to discuss how we can act together in order to deal with the unaccountable wickedness of the Silicon Valley oligarchs.”

Watson also criticised British news sites for running the Christchurch attacker's footage and manifesto. "It’s deeply concerning and irresponsible that mainstream news sites are giving a platform to the hateful extremist violence that has devastated so many lives, particularly after the New Zealand authorities have asked for the footage not to be shared," he said.

Mail Online's main story on the terrorist attack featured an edited version of the terrorist's video, showing him approaching one of the mosques and drawing his weapon. The pop-up video also followed the reader down the page.

In another story that focused on the terrorist's manifesto, the website uploaded a PDF of the document in full, allowing readers to read and download it. The embed was later removed after BuzzFeed News approached the publication for comment.

The Mail initially declined to comment. But a spokesperson later released a statement claiming the publication of the manifesto was "an error and swiftly corrected".

"As with all incidents of terror, news organisations have to strike the right balance between showing the public what has happened — and why — and playing into the terrorists’ hands," the Mail's spokesperson said.



"In common with many other news organisations around the world, MailOnline carried for a time a very short excerpt from beginning of the Christchurch mosque gunman’s video that showed no violence or victims.

"On further reflection, we decided to remove it some hours ago."