A class action lawsuit lodged in the US has accused Apple of deliberately crippling old iPhones to force users to upgrade to newer models.

Lead plaintiff Chaim Lerman of Brooklyn alleged the tech giant breached New York state law by telling owners of the fifth generation iPhone 4s to upgrade to the “buggy” iOS 9, according to a court document obtained by AppleInsider.

His phone allegedly “significantly slowed down” and became “no longer functional for normal use” after the download – complaints that would sound familiar to many Australian iPhone users.

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When Apple released the September update, it claimed it to be compatible with the old iPhone 4s, 5, 5c, 5s, 6 and 6 Plus. But many Australians complained on social media that their phones slowed down, froze and crashed more often after the download, with no way to revert back to the old software.

Apple made big claims about iOS 9.

The New York case echoes all these concerns.

“The update significantly slowed down their iPhones and interfered with the normal usage of the device, leaving Plaintiff with a difficult choice: use a slow and buggy device that disrupts everyday life or spend hundreds of dollars to buy a new phone,” the class action lawyers wrote to the court.

Many Australian phone users continue to use old iPhones, or hand them down to other family members. The longevity of the hardware is a testament to Apple’s engineering. But without functional software, the phones are useless.

A spokesperson for the company in Australia declined to comment on the allegations.

Was this a devious plan to boost sales of the new iPhone 6s and 6s Plus, released in September? That’s what the class action, overseen by New York firm Bronstein, Gewirtz & Grossman, suggests.

The central allegation of the case is that Apple encouraged all its iPhone 4s customers in New York, and indeed across the world, to upgrade to iOS 9 despite knowing full well (presumably from software testing) that the upgrade was full of bugs, amounting to deceptive trade practice and false advertisement.

Apple eventually fixed many of the bugs. But had users already bought new phones?

The plaintiffs don’t need to prove that Apple did this deliberately – they can simply argue the company envisaged this outcome, or should have foreseen it. But their case raises the possibility that it was indeed intentional.

“Apple clearly wants and encourages everyone to update to the latest iOS version because it helps its image, marketing position, ability to sell new devices, and bottom line,” the lawyers wrote.

“At all relevant times, Apple knew its statements and advertisements to be materially misleading. Their statements and advertisements were negligent, reckless and/or intentional.”

It’s not the only legal woe for the company this week. Its Italian subsidiary agreed to pay Italian authorities the equivalent of $A713 million in allegedly unpaid taxes, La Repubblica reported on Wednesday.

If the New York case is heard by a court, and the allegations proven, it could be a big step forward for thrifty iPhone users who cling to older models as long as they can. Any change Apple makes to software updates to minimise legal risk is likely to be consistent across the globe.

If they keep rolling out updates for older devices, but pay closer attention to the specs for fear of being sued again, then Apple lovers will be the winners.

Mr Lerman is suing on behalf of multiple iPhone 4s owners.

Sadly, this is unlikely. Most corporate law cases in the US, as in Australia, settle before they reach a court verdict.

The lawsuit seeks more than $US5 million in damages to be split between more than 100 plaintiffs. (The exact damages sought and total number of plaintiffs were not specified in the court document.) Apple’s lawyers will probably agree to a lump sum payout.

So, Australians can’t join the case, nor are we likely to ever see the benefits of a court verdict. But hey, at least we can play judge and jury.

Do you think Apple knew, or should have known, the update was going to slow down the iPhone 4s? And if so, should it have warned us? Tell us in the comments below.

The New Daily contacted Apple Australia for comment.