The tech giant may be forced to permit competing application marketplaces within the United Kingdom.
The iPhone maker could be required to permit competitors to run separate app stores on iPhones across Britain, after a decision from the market watchdog.
This represents a major shift to Apple's infamous "walled garden" where apps can only be installed from its own official marketplace.
But the Competition and Markets Authority has designated both Apple and Google as having "strategic market status" - effectively saying they have significant control over smartphone ecosystems.
Watchdog Findings
The CMA said the tech firms "could be restricting innovation and competition".
But the regulator clarified it did not "find or assume wrongdoing" from the companies.
"Mobile applications generates one and a half percent of the UK's GDP and supports around four hundred thousand positions, which is why it's crucial these sectors function properly for enterprises," stated a top executive from the competition authority.
Approximately ninety to one hundred percent of UK mobile devices run on the two tech companies' mobile platforms, creating what the authority calls an "virtual monopoly".
Based on current data, nearly half of British smartphone users use an Apple device - which runs the iOS operating system - with the overwhelming bulk of the remaining users using Google's Android.
Apple's Reaction
The regulatory probe focused on how prominent the companies' own applications are versus rivals - as well as their browsers and platform software.
It is unknown what changes the regulator will seek to implement, but earlier it published guidelines outlining possible actions it could take.
These include mandating it to be easier for people to switch between Apple and Android phones, and for both companies to list applications "in a fair, objective and transparent manner" in their marketplaces.
Apple particularly may be required to allow alternative app stores on its devices, and enable people to download programs directly from companies' websites.
This would follow comparable regulations in the EU, which previously took action against Apple for restrictive practices.
The technology firm cautioned the United Kingdom could face delays to getting new features - as has occurred in the EU - which the organization attributes to heavy regulation.
For example, some AI features which have been launched in other regions are not accessible in the European market.
"Apple encounters intense rivalry in every market where we operate, and we strive continuously to create the finest offerings, services and user experience," the company said in a release.
"Britain's implementation of European regulations would undermine that, leaving users with reduced data protection and safety, delayed access to new features, and a fragmented, more complicated user journey."
Google's Standpoint
Android users can currently use third-party app stores - though critics say they are not as user-friendly as the company's official Play Store.
The regulator's plan said the search company may have to "modify the interface" of installing applications straight from websites, as well as "remove user frictions" when using third-party platforms.
"There appears to be no the justification for today's designation decision," a Google competition lead stated.
The executive said "most" of Android users use third-party platforms or download apps straight from a developer's website, and asserted there is a much wider selection of apps offered for Google device owners compared to those on Apple devices.
"Currently available are 24,000 Google-compatible devices from thirteen hundred phone manufacturers worldwide, facing strong rivalry from Apple's platform in the UK," the spokesperson added.
Android is an freely available software, which means creators can utilize and develop on top of it for free.
The company argues this means it promotes competition.
But advocacy organizations said restrictions on these firms' dominance in other countries "are already helping businesses to develop and providing consumers more options".
"Their dominance is now causing real harm by restricting choice for users and competition for businesses," stated a policy expert.