The Daily Mail's website uploaded the Christchurch mosque attacker's 74-page "manifesto", allowing readers to download the entire document just hours after the massacre on Friday which left at least 49 people dead.
The Mail was one of several British news outlets that defied requests from New Zealand police on Friday not to spread the terrorist's first-person footage, which had been repeatedly shared across social media platforms in the wake of the attack.
In the immediate aftermath of the attack, YouTube, Twitter, Facebook, and Reddit said they were working to remove the attacker's videos from their platforms. The footage kept appearing in and disappearing from search results.
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."
Another red-top tabloid, the Sun, showed edited footage from the video, with a GIF featured in the centre of the website's homepage. The GIF looped the terrorist approaching the mosque and drawing his firearm before the attack.
Both publications also prominently featured digital advertisers alongside the footage.
A spokesperson for the Sun defended running footage from the video, claiming the the parts of the video the website decided to run didn't "depict any actual violence".
“We recognise that in the aftermath of horrific events such as these there will be sensitivities around reporting, and we take those responsibilities seriously," the spokesperson said in a statement. "We have thought long and hard about how much of the easily available material currently on social media we should host on our site in order to shed light on this barbarous attack and the twisted ‘motive’ behind it.
"We have not published any video which depicts any act of actual violence, nor have we published or linked to the hate-filled manifesto.”
The Daily Mirror's story ran edited video which showed several minutes of the attack, including the terrorist driving, changing weapons from his car, and shooting at people on the street.
After the video had been up for several hours, a Mirror source said there was "senior intervention" at the publication and it was taken down. Lloyd Embley, the publisher of the Daily Mirror, later tweeted that it's "not in line with our policy relating to terrorist propaganda videos".
Australian media outlets also ignored requests from police, with the country's Sky News channel and 10 Daily website including the first-person video in their coverage of the attack.
On Friday, New Zealand's prime minister Jacinda Ardern said the attack represented "one of New Zealand's darkest days". A man in his twenties has been charged with murder and will appear in court in Christchurch on Saturday morning.