TikTok is facing a London lawsuit over privacy issues on behalf of millions of children in the U.K. and Europe.

Anne Longfield, the former Children's Commissioner for England, has filed a legal claim against TikTok for allegedly illegally accessing the personal information of millions of children. The case is part of a class-action lawsuit.

TikTok and its parent company, ByteDance, are accused of "deliberately violating U.K. and EU children's data protection law." They specifically claim that TikTok does not have consent to take and process children's data, and that it collects that data without adequate warning.

Longfield, who is supporting the claim by law firm Scott + Scott, wants TikTok to remove the details of its U.K. and European child users and to pay them compensation.

"TikTok is a data collection service that is thinly-veiled as a social network," Longfield said. "It has deliberately and successfully deceived parents, whose best intentions are to protect their children and children themselves."

TikTok, according to Longfield and Scott + Scott, collects children's phone numbers, videos, pictures, and location, as well as biometric data. The suit claims that every child user who has used TikTok since May 25, 2018, has had their data collected in this manner.

According to internal data obtained by The New York Times, 43% of TikTok users were 14 or younger as of spring 2020. At the time, one in every three German users was thought to be under the age of 14, as were 45% of French users.

Longfield further claims that TikTok's company structure, which has a European headquarters in London which reports into a Cayman Islands-located parent company, is "deliberately opaque".

The lawsuit was filed in December, but the specifics were only revealed Wednesday. If the case is successful, children may be entitled to compensation worth thousands of pounds. Claimants say that more than 3.5 million children are affected in the U.K. alone, suggesting a potentially large bill for the app if it loses.

TikTok was fined $5.7 million by the U.S. Federal Trade Commission in February 2019 for the way the app it purchased, Musical.ly, handled children's data. South Korea's media watchdog fined TikTok $155,000 for collecting the data of 6,000 children under the age of 14 in July 2020.