Apple Inc (NASDAQ:AAPL) and Alphabet Inc (NASDAQ:GOOG) Google's dominance of mobile browsers, as well as the iPhone maker's restrictions on cloud gaming through its app store, are being investigated by Britain's competition watchdog.
The Competition and Markets Authority (CMA) said it would also take action against Google's app store payment practices.
The CMA said the two tech giants had a stranglehold over operating systems, app stores, and web browsers on mobile devices due to their "effective duopoly" on mobile ecosystems.
"When it comes to how people use mobile phones, Apple and Google hold all the cards," CMA chief executive Andrea Coscelli said in response to the publication of a report on mobile ecosystems.
"As good as many of their services and products are, their strong grip on mobile ecosystems allows them to shut out competitors, holding back the British tech sector and limiting choice."
In Britain last year, 97% of mobile web browsing was powered by Apple or Google search engines, and Apple also banned other browsers from iPhones, added the CMA.
That would severely limit rival browsers' ability to differentiate themselves from Apple's Safari on speed and functionality.
Apple said it had "created a safe and trusted experience users love and a great business opportunity for developers" with its ecosystem.
"We respectfully disagree with a number of conclusions reached in the report, which discount our investments in innovation, privacy and user performance, all of which contribute to why users love iPhone and iPad and create a level playing field for small developers to compete on a trusted platform," a spokesperson said.
"We will continue to engage constructively with the CMA to explain how our approach promotes competition and choice, while ensuring consumers privacy and security are always protected."
Google, on the other hand, said its smartphones offers more choice than any other mobile platform with its Android operating system and its Google Play app store has played host to millions of apps.
"We regularly review how we can best support developers and have reacted quickly to CMA feedback in the past," a Google spokesperson said.
Market investigation consultation is to close on July 22.