Apple is facing a backlash from customers over a software update that disables iPhone 6 handsets if it detects repairs by third-party technicians.
The problem, known as "error 53", is reportedly rendering thousands of devices permanently useless.
The Guardian reported that at least one firm of US lawyers is now considering a class action.
It said users claimed their phones were disabled after the software update detected a repair had been carried out by a non-Apple technician on the handset's home button, which has touch ID fingerprint recognition built in.
Apple has said the the error message is a security measure taken to prevent fraudulent transactions.
"We take customer security very seriously and error 53 is the result of security checks designed to protect our customers. iOS checks that the Touch ID sensor in your iPhone or iPad correctly matches your device's other components," it said in a statement.
"If iOS finds a mismatch, the check fails and Touch ID, including for Apple Pay use, is disabled. This security measure is necessary to protect your device and prevent a fraudulent Touch ID sensor from being used.
The Guardian reported at least one firm of US lawyers said it hopes to bring a class action against the technology giant on behalf of people whose phones have been rendered worthless the software upgrade.
Many iPhone 6 customers have been discussing error 53 online.
I got my car repaired by the local garage and now it doesn't start. I guess I'll just go buy a new car. #error53— Tony Murray (@MrTweetTastic) February 5, 2016
Umm, people do realize that if you allowed the TouchID to get replaced, you could hack the phone, right? It's a security feature. #Error53— Hampton on Hampton (@hcatlin) February 6, 2016
Apple is basically the insecure boyfriend of tech. Self-destroying their phones if you even talk to another phone repair company. #Error53— Ben Powless (@BenPowless) February 6, 2016
At Apple's discussion forums, one user named wallihall wrote: "With this update I'm unable to use the phone, and still have to pay for the phone itself.
"I did get the front screen replaced, and I understand that it's now considered "tampered with", but at least let me use my iPhone on the old IOS system... I can't retrieve old photos or important documents I once had."