Google could face a compensation bill of up to £3.3bn over claims it harvested personal data, including political views and health information, from more than four million Britons without their permission.

Google is alleged to have unlawfully gathered and shared the personal ­information of millions of iPhone users in the UK by bypassing the default ­privacy settings on the Apple device between June 2011 and February 2012. The High Court is due to issue a ruling on the claims today.

Claimants allege Google violated ­iPhone privacy by effectively tricking devices into releasing personal data from the Safari web browser. This has become known as the “Safari Workaround”.

The collective High Court action is led by former Which? director Richard Lloyd. Hugh Tomlinson QC, of Matrix Chambers, is representing Mr Lloyd alongside law firm Mishcon de Reya.

Mr Lloyd and legal experts believe Google breached Section 4 of the Data Protection Act 1998. Under Section 13 of the Act individuals can claim compensation for breaches of the Act.

The group told the courtthat data collected included race, physical and mental health, political leanings, sexuality, social class, financial, shopping habits and location data.

Mr Lloyd set up a consumer campaign called Google You Owe Us as part of this legal action. The group now has 20,000 people as co-claimants.

The compensation bill, if claimants are successful, would be the largest ever owed to British consumers over improper use of data.

The campaign group says Google could be forced to pay £750 to each user affected. At the time of launching the claim, Mr Lloyd said he wanted to “send a strong message” to Google and other tech giants in Silicon Valley. “We’re not afraid to fight back if our laws are ­broken,” he said.

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Anthony White QC, for Google, said in a hearing earlier this year that the purpose of Mr Lloyd’s claim was to ­“pursue a campaign for accountability and retribution” against the company, rather than seek compensation for ­affected individuals.

Mr White said: “The court should not permit a single person to co-opt the data protection rights of millions of ­individuals for the purpose of advancing a personal ‘campaign’ agenda and should not allow them to place the onus on individuals who do not wish to be associated with that campaign to take positive steps to actively disassociate themselves from it.”

Google is also facing a lawsuit over its location tracking technology.

The tech giant was accused of illegally tracking the movements of ­iPhone and Android mobile users even if they had switched off their location services.

Earlier this year, Google was hit with a record £2.14bn fine from the European Union after a seven-year investigation into claims the technology giant abused its internet search monopoly.

The penalty is the biggest ever competition fine from the European Commission, doubling the previous record handed to Intel in 2009.

The EU said Google had broken EU competition law by exploiting the power of its search engine to promote its online shopping service at the expense of other price-comparison sites. Google declined to comment.