A Spanish anti-disinformation foundation accused TikTok on Monday of not doing enough to prevent paedophiles from accessing child sexual abuse material or soliciting images from children on the platform.
"Material you would expect to find only on the dark web is on TikTok," the Maldita.es association said.
In the investigation published Monday, Maldita.es catalogued more than 1,000 videos of child abuse footage, which had been viewed a total of 48 million times.
"The findings of this investigation seriously call into question the effectiveness of TikTok's measures against child abuse, and also point directly to its platform features being actively exploited by child predators," the association said.
TikTok was yet to reply to an AFP request for comment.
According to Maldita.es, TikTok removed only one-tenth of the content it had flagged and blocked just 26 percent of illegal posts in Spain.
The widely popular platform, owned by Chinese parent company ByteDance, faces a wave of lawsuits and investigations over accusations that it has failed to protect minors, which the company has frequently denied.
On Friday, the EU told TikTok to change the "harmful" design of its personalised For You feed or risk large fines under the bloc's digital content rules.
