An investigation launched in January by the Italy’s Competition Authority found that smartphone software updates had a negative effect on the performance of the devices.

It is the first ruling of its kind against smartphone manufacturers, the investigation followed accusations operating system updates for older phones slowed them down and encouraged users to buy new phones.

In a statement the antitrust watchdog said: “Apple and Samsung implemented dishonest commercial practices” and that operating system updates “caused serious malfunctions and significantly reduced performance, thus accelerating phones’ substitution.”

It added the two firms had not provided clients adequate information about the impact of the new software “or any means of restoring the original functionality of the products”.

Samsung told owners of its Galaxy Note 4 phone to install a new version of Google’s Android operating system intended for the more recent Galaxy Note 7, but which users claimed rendered the old model sluggish.

Apple told iPhone 6 owners to install an operating system designed for the iPhone 7, leading to problems for owners of the older model.

Both firms were issued the maximum fine of €5 million each and ordered to display a notice on their Italian websites informing customers of the watchdog’s decision.

The fine to Jobs’ Mob was doubled because it did not give its users clear information about “essential” characteristics of lithium batteries, including their average life expectancy, how to maintain them or eventually replace them in the firm’s iPhones.

Apple acknowledged in December that it had intentionally slowed iPhones with degraded batteries through software updates to avoid sudden shutdown problems but denied it had ever done anything to intentionally shorten the life of a product.

The company later apologised for its actions and reduced the cost of battery replacements. It also added battery health information to iOS and allowed users to turn off the slowing down of the iPhone’s processor.

A Samsung spokesperson said the company was disappointed by the decision and intends to appeal the fine: “Samsung did not issue any software update that reduced the Galaxy Note 4’s performance. In contrast, Samsung has always released software updates enabling our customers to have the best experience possible.”

Apple is saying nothing, but its normal procedure is to say it is not guilty all the way through the legal system.