"We're concerned the rules the UK is now considering would undermine the privacy and security protections that our users have come to expect, hamper our ability to innovate, and force us to give away our technology for free to foreign competitors," an Apple spokesperson said.
"We will continue to engage with the regulator to make sure they fully understand these risks."
Google's Senior Director of Competition Oliver Bethell said it was "crucial that any new regulation is evidence-based, proportionate and does not become a roadblock to growth in the UK."
He added the Android operating system, Chrome browser and Play app store "enable great choice, security and innovation for users".
"We remain committed to constructive engagement with the CMA for the duration of this process," he added.
Android and Blink, the engine which powers the Chrome browser, are open source, which means developers can use their underlying code for free.
Google's view is this enables greater competition and allows for cheaper products to be made.
Consumer rights group Which? welcomed the probe from the regulator.
"While these companies have driven innovation, their dominance is now causing real harm to consumers and to the businesses that depend on them," said Rocio Concha, director of policy and advocacy.