The tech giant could be compelled to permit rival app stores in UK.
The iPhone maker could be required to permit competitors to run their own application platforms on Apple devices across Britain, after a decision from the competition regulator.
This would be a significant change to Apple's well-known "walled garden" where apps can only be installed from the company's App Store.
But the UK competition watchdog has designated both Apple and Google as having "dominant market position" - effectively saying they have significant control over smartphone ecosystems.
Watchdog Assessment
The regulator said the two companies "may be limiting innovation and market rivalry".
But the regulator clarified it did not "determine or presume wrongdoing" from the firms.
"The app economy contributes one and a half percent of the British economy and supports around four hundred thousand positions, which is why it's crucial these markets function properly for enterprises," stated a top executive from the CMA.
Around ninety to one hundred percent of British smartphones run on the two tech companies' operating systems, creating what the authority calls an "effective duopoly".
Based on recent analysis, nearly half of British smartphone users own an Apple device - which runs the iOS operating system - with the overwhelming bulk of the remaining users using Google's Android.
The Company's Reaction
The regulatory probe focused on how dominant the companies' own applications are versus competitors - as well as their web applications and operating systems.
It is unclear what changes the authority will seek to implement, but previously it published guidelines detailing possible actions it could take.
These include requiring it to be more straightforward for people to switch between Apple and Android phones, and for both firms to list applications "fairly and openly" in their marketplaces.
Apple particularly may be required to permit third-party marketplaces on its devices, and let people to download programs directly from companies' websites.
This would follow a similar ruling in the EU, which previously took action against the company for anti-competitive behaviour.
Apple warned the United Kingdom could face delays to getting new features - as has occurred in the EU - which the company attributes to strict rules.
For example, some AI features which have been rolled out in other parts of the world are not available in the European market.
"Apple encounters fierce competition in every market where we do business, and we strive continuously to create the finest offerings, solutions and user experience," the company said in a release.
"The UK's adoption of European regulations would weaken that, leaving users with weaker privacy and safety, slower availability to new features, and a fragmented, less seamless user journey."
Google's Position
Google device owners can presently use third-party app stores - though commentators say they are not as user-friendly as Google's own Play Store.
The regulator's plan said Google may have to "change the user experience" of installing applications straight from websites, as well as "eliminate barriers" when using third-party platforms.
"We simply do not see the justification for today's designation decision," a company competition lead stated.
The representative said "most" of Android users use alternative app stores or install applications straight from a developer's website, and claimed there is a much wider selection of applications offered for Android users versus those on Apple devices.
"There are now 24,000 Google-compatible devices from thirteen hundred device makers globally, facing intense competition from iOS in the United Kingdom," the spokesperson continued.
Google's platform is an freely available software, which means creators can utilize and develop on top of it for free.
The company contends this means it promotes competition.
But consumer groups said restrictions on these firms' dominance in different nations "are already helping enterprises to innovate and providing customers more choice".
"Their dominance is now creating genuine problems by restricting choice for consumers and market rivalry for companies," stated a consumer advocate.