The UK competition regulator has opened an in-depth investigation into Microsoft’s $75bn acquisition of video game maker Activision Blizzard, the creator of blockbuster Call of Duty.

The Competition and Markets Authority on Thursday referred the tie-up for a phase 2 probe, having raised concerns that the deal could hurt rivals such as Sony and present a threat to open competition in new markets such as cloud gaming.

The watchdog has appointed an independent panel that will examine the deal in greater depth and analyse the competition implications.

The decision comes after the Financial Times revealed that Microsoft had not offered any potential solutions to the regulator’s antitrust concerns at the end of its phase 1 investigation earlier this month.

The CMA was the first global regulator to raise concerns about the blockbuster deal, which is Microsoft’s biggest and would make it the third-largest gaming company in terms of revenues.

At the end of its phase 1 investigation, the CMA said it was concerned that Microsoft could use its control over games such as Call of Duty, which has brought in $30bn in lifetime sales for Activision, and World of Warcraft to harm its rivals.

Microsoft said it would continue to ensure equal access to Call of Duty and that it would remain available on consoles such as PlayStation as well as Microsoft’s Xbox.

The FT previously revealed that the deal was facing in-depth probes in both Brussels and London, following concerns that the tie-up was anti-competitive and would exclude rivals from accessing games.