"Following our Phase 1 investigation, we are concerned that Microsoft could use its control over popular games like Call of Duty and World of Warcraft post-merger to harm rivals, including recent and future rivals in multi-game subscription services and cloud gaming," said Sorcha O'Carroll, senior director of mergers at the CMA.
"If our current concerns are not addressed, we plan to explore this deal in an in-depth Phase 2 investigation to reach a decision that works in the interests of UK gamers and businesses."