Apple is facing a £750 million (878 million euros, $918 million) lawsuit in Britain after a consumer rights champion on Thursday filed a claim accusing the US tech giant of secretly slowing down older iPhone models.  

Justin Gutmann says Apple "throttled" the performance of older iPhone handsets after users installed upgrades that they were told would improve the performance of their device.

He claims Apple never told users that the update could slow their device and that the tool was introduced to mask the inability of older iPhone batteries to cope with the demands of newer operating systems. 

Apple said in a statement that "we have never -- and would never -- do anything to intentionally shorten the life of any Apple product, or degrade the user experience to drive customer upgrades. 

"Our goal has always been to create products that our customers love, and making iPhones last as long as possible is an important part of that," it added.

Gutmann's claim with the Competition Appeal Tribunal seeks damages for 25 million iPhone users to the tune of £768 million.

The complaint revolves around a power management tool included in a 2017 software update, which slowed down older iPhone models and prevented abrupt shutdowns as they struggled with the overhead of a new operating system.

Gutmann says Apple never told users that the update could slow a user's device and claims the tool was introduced to prevent costly repairs or recalls. 

"Instead of doing the honourable and legal thing by their customers and offering a free replacement, repair service or compensation, Apple instead misled people by concealing a tool in software updates that slowed their devices by up to 58 percent," said Gutmann.

"I'm launching this case so that millions of iPhone users across the UK will receive redress for the harm suffered by Apple's actions".

Apple apologised at the time and said it would replace batteries at cut price and would allow users to turn off the power management tool manually.

It has faced legal action in several countries over the issue and agreed to pay up to $500 million to owners of older models in the United States in 2020. 

French authorities fined the group 25 million euros in the same year for failing to warn that updates could slow down older models.

The claim seeks compensation for owners of the iPhone 6, 6 Plus, 6S, 6S Plus, SE, 7, 7 Plus, 8, 8 Plus and iPhone X models.