By Muvija M

LONDON (Reuters) -Britain's competition regulator said it plans to designate Apple ( AAPL ) and Google with so-called strategic market status for their role in mobile ecosystems, as it steps up scrutiny of what it has described as their duopoly.

The plans announced on Wednesday follow findings by an inquiry group at Britain's Competition and Markets Authority (CMA) that a number of markets relating to mobile internet browsers were not working well for consumers or businesses.

Apple's ( AAPL ) Safari and Google's Chrome dominate the mobile browser market on iPhones and Android devices, respectively.

"Apple ( AAPL ) and Google's mobile platforms are both critical to the UK economy ... but our investigation so far has identified opportunities for more innovation and choice," CMA head Sarah Cardell said in a statement.

"The targeted and proportionate actions we have set out today would enable UK app developers to remain at the forefront of global innovation while ensuring UK consumers receive a world-class experience."

A final decision on both the designations will be made by October 22, the statement said. The regulator also published roadmaps on potential further action as part of these parallel investigations.

A strategic market status (SMS) designation allows the CMA to impose interventions on a firm, such as requiring it to adhere to specific behaviour so as not to undermine fair competition.

Both Apple ( AAPL ) and Google pushed back against the CMA's proposals, with Google calling the step "disappointing and unwarranted."

"It is ... crucial that any new regulation is evidence-based, proportionate and does not become a roadblock to growth in the UK," Google's senior director for competition, Oliver Bethell, said.

Apple ( AAPL ) said separately it was concerned that the new rules being considered would undermine the privacy and security protections expected by its users.