Alphabet's Google faces a multibillion-dollar lawsuit in the UK over claims that YouTube routinely breaks privacy laws by tracking children online.

The suit, filed on behalf of more than 5 million British children under 13 and their parents, is being brought by privacy campaigner Duncan McCann and being supported by Foxglove, a tech justice group. The claimants estimate that if they're successful, there would be as much as 2.5 billion pounds ($3.2 billion) in compensation, worth between 100 to 500 pounds per child.

The filing alleges that YouTube's methods of targeting underage audiences constitute "major breaches" of UK and European privacy and data rules designed to protect citizens' control over their own private information. YouTube has "systematically broken these laws by harvesting children's data without obtaining prior parental consent," it alleges.

A spokesperson for YouTube declined to comment on the lawsuit Monday but added that the video streaming service isn't designed for users under the age of 13.

"We launched the YouTube Kids app as a dedicated destination for kids and are always working to better protect kids and families on YouTube," the company said in an emailed statement.

Privacy watchdogs have in recent months turned their attention more closely to the protection of children's data, with regulators in Ireland looking to clarify the rights of children under the European Union's strict data protection rules, and the UK's Information Commissioner publishing a code of practice with specific standards for online services to follow.

ByteDance Ltd.'s social media app TikTok has in recent months also come under scrutiny by several EU data watchdogs over its processing of children's data.

It's the first class action suit in Europe brought against a tech firm on behalf of children, according to the claimants. The legal action is being backed by Vannin Capital, a global litigation funder.

"The cost of YouTube's so-called free service is kids that are addicted to online content and influenced by large tech companies that have stolen their privacy," Cori Crider, director of Foxglove, said. "Google won't clean up its act until it's forced to do so by the courts."