Sarah Tew/CNET

Apple's controversial iPhone slowdown is drawing legal fire.

A pending lawsuit against Apple says a software tweak that slows some older iPhones to counteract problems found in aging batteries is a fraud designed to spur upgrades to the latest model.

Apple didn't immediately respond to a message seeking comment.

After years of complaints from consumers that their iPhones seem slower once a new model is released, Apple on Wednesday disclosed it was indeed slowing the performance of some older iPhones under particular circumstances. When batteries age, become very cold or operate at low power, their currents can spike when the phone's computer tries to hit higher speeds. Rather than having a phone shut down automatically to protect itself, Apple said that last year it tweaked its iOS software for some older iPhones so they slow down instead.

Now playing: Watch this: Yep, Apple slows down older iPhones

The lawsuit, filed Thursday in the Northern District of Illinois, Eastern division, represents five people who allege the company purposefully updated the phones' operating system to dampen its performance as a way of "fraudulently forcing iPhone owners to purchase the latest model from Apple," according to a release from attorney James Vlahakis of Lombard, Illinois-based Atlas Consumer Law.

Two additional lawsuits were also filed Thursday in the Central District of California and the Northern District of California. Both of those suits allege largely the same thing -- that Apple knowingly misled consumers about battery problems in an effort to get them to upgrade to the latest iPhone models.

The plaintiffs in the three cases allege updates to the iPhone 5, iPhone 6, iPhone 7 and 7 Plus all caused slowdowns in performance.

Apple's disclosure this week didn't include the iPhone 5. The company said the software update applied to the iPhone 6 and 6 Plus, 6S and 6S Plus and SE, and earlier this year was extended to the iPhone 7 and 7 Plus. It will be applied to other Apple devices in the future, the company said.

In the past, Apple has routinely said it doesn't purposely slow phones to encourage customers to replace them. Apple said in a statement earlier this week that the goal of the battery-related slowing was "to deliver the best experience for customers."

First published Dec. 22, 8:25 a.m. PT.

Update, 2 p.m. PT: Adds information on additional lawsuits.

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