Last week, a separate document released by a tech watchdog group showed the Texas attorney general might sue Apple for such violations in connection with a multi-state probe, without specifying charges.

The attorney general offices in Arizona and Texas declined to comment. Apple did not respond to a request for comment.

Apple came under fire in 2017 when Primate Labs, the maker of software for measuring a phone's processor speeds, revealed that some iPhones became slower as they aged.

Apple later acknowledged that it reduced power demands - which can slow the processor - when an ageing phone's battery struggles to supply the peak current the processor demands. Apple said without its adjustments, iPhones would have unexpectedly shut down from power spikes.

iPhone users said that appeared to confirm long held suspicions that Apple slowed older devices to encourage users to buy new phones. Apple publicly apologised and slashed prices on battery replacements.

Earlier this year, Apple agreed to pay up to $500 million to settle a proposed class action lawsuit related to the battery issues.