Google illegally gathered the personal data of millions of iPhone users in the UK, according to a collective lawsuit led by a former director of the consumer group Which?

Richard Lloyd, a veteran consumer rights campaigner, alleges the technology company bypassed the default privacy settings on Apple phones and succeeded in tracking the online behaviour of people using the Safari browser.

Google then allegedly used the data in its DoubleClick advertising business, which enables advertisers to target content according to a user’s browsing habits.

The lawsuit, filed in London’s High Court, alleges Google’s tactic, known as “the Safari Workaround”, breached the UK Data Protection Act by taking personal information without permission.

“In all my years speaking up for consumers, I’ve rarely seen such a massive abuse of trust where so many people have no way to seek redress on their own,” said Mr Lloyd, who has set up a group called Google You Owe Us.

Google said: “This is not new — we have defended similar cases before. We don’t believe it has any merit and we will contest it.”

Google has already paid millions of dollars to US states and the US Federal Trade Commission over the Safari security bypass.

The case is the first time such a collective action — where one person represents a group with a shared grievance, akin to a US-style class action — has been brought in Britain against a leading tech company over alleged misuse of data.

Roughly 5.4m people in Britain had an iPhone between June 2011 and February 2012 and could be eligible for compensation, according to the claim.

Mr Lloyd has secured £15.5m in backing from Therium, a company that funds litigation and has previously backed group claims such as the consumer action against Volkswagen in the scandal over diesel emissions.

The funds cover Mr Lloyd’s legal costs — he is being advised by the firm Mishcon de Reya — as well as insurance in case he loses and has to pay Google’s legal bills.

Although the size of any potential payout would be determined by the court, Mr Lloyd said he expected each claimant would receive several hundred pounds.

“We think there is a massive gap in the law in terms of consumer redress around data rights being breached,” he said. He hoped the battle would end up producing “a clear set of guidelines and precedent” for consumers as to how they could act collectively in similar cases.

Should Mr Lloyd win, those who can prove they were affected by the alleged data breach are likely to have several years to make a claim.

The case will be closely watched by consumer groups and data protection lawyers, with the control, use and security of personal information coming under increasing scrutiny.

In addition, new regulations coming into force across the EU next year include a provision for anyone whose data has been misused to instruct consumer protection groups to bring claims on their behalf.