A consumer activist launched Thursday a lawsuit accusing Google of illegally collecting data on more than five million British iPhone users, who could possibly see a payout reaching into the hundreds of millions.
A campaign group dubbed 'Google You Owe us' says the tech giant owes consumers "trust, fairness and money" after unlawfully placing cookies on mobile phones between 2011 and 2012.
"Through this action, we will send a strong message to Google and other tech giants in Silicon Valley that we're not afraid to fight back if our laws are broken," said Richard Lloyd, who is spearheading the legal action.
A former government adviser and executive director of consumer rights group Which?, Lloyd says he has "rarely seen such a massive abuse of trust where so many people have no way to seek redress on their own".
Google is thought to have bypassed the default privacy settings of Apple's Safari Internet browser using a technique dubbed 'the Safari Workaround', planting cookies into phones before selling the information they collect to advertising network 'DoubleClick Service'.
A cookie is a small file stored in a phone or computer which allows for the tracking of an individual's browsing activity, information which is valuable to advertisers as it allows them to better target ads to interested consumers.
EU directives require consumers to be asked for consent before cookies are installed on their devices and used to transfer their data.
Google however denies that it acted illegally, saying it has defended similar cases in the past.
"We don't believe it has any merit and we will contest it," a Google spokeswoman commented on the case.
The lawsuit is being brought on behalf of roughly 5.4 million iPhone users who were resident in England and Wales at the time and could have been affected.
Although they could each get several hundreds of pounds if the case were to be succesful, the group says its objective is as much about accountability as compensation.
A similar case brought by three individuals to the English High Court in 2015 was settled confidentially, but "opened the door" in principle to a new case, according to Google You Owe Us.
The group says its suit is the first collective action of its kind against a major tech company for misuse of personal data.
It is expected to be brought to court early next year, although no date has yet been set for a hearing.
Google You Owe Us said the case is being financed to the tune of GBP 15.5 million ($20.9 million, EUR 17.6 million) by Therium, an outfit which funds litigation efforts in exchange for a share of any award.