The former children's commissioner for England, Anne Longfield, says that behind TikTok's fun songs and dances "lies something far more sinister.

TikTok was hit with a legal claim in Britain on Wednesday accusing the video-sharing app of illegally collecting personal data from millions of children in Europe.

The former 's commissioner for England, Anne Longfield, and law firm Scott + Scott have brought the case against the firm and its Chinese parent group ByteDance on behalf of children aged under 13 in the UK and under 16 in the European Economic Area, a statement said.

TikTok said separately that it would "vigorously defend" itself, noting that privacy and safety were "top priorities" for the platform.

The "alleges that TikTok and ByteDance have violated UK and EU children's data protection law (GDPR), and deceived parents about how exposed their children's is when they use the app".

The case affects potentially more than 3.5 million children in the UK alone, the statement added.

"TikTok is a hugely popular social media platform that has helped children keep in touch with their friends during an incredibly difficult year," Longfield noted.

"However, behind the fun songs, dance challenges and lip-sync trends lies something far more sinister."

She added that "parents and children have a right to know that private information, including phone numbers, physical location, and videos of their children are being illegally collected".

The claim seeks to "put a stop to TikTok's shadowy data collection practices", Longfield said, as she demanded that the platform deletes all private information "illegally processed" when the app is used by children.

The case aims to win compensation that could run into billions of pounds, the statement added.

TikTok in response maintained it has "robust policies, processes and technologies in place to help protect all users, and our teenage users in particular.

"We believe the claims lack merit and intend to vigorously defend the action," it added in a statement.

The claim stated that every child that has used TikTok since May 2018, regardless of whether they have an account or the nature of their privacy settings, may have had their private personal information illegally collected by ByteDance through TikTok for the benefit of unknown third parties.

The claim also referred to recent hefty fines handed down to TikTok in the United States and South Korea following child data cases.