In brief: The ongoing saga of Microsoft's acquisition of Activision Blizzard is showing no signs of ending soon. The latest spat involves the UK watchdog's investigation of the $69 billion deal, which Redmond says is being influenced by Sony.

Last month brought news that the United Kingdom's Competition and Markets Authority (CMA) feared that Microsoft's purchase of Activision Blizzard could lead to competition concerns within the video game industry. The regulator said that if Microsoft didn't submit a proposal to assuage these worries, the CMA would open an extended stage 2 phase of its probe in which the acquisition would face increased scrutiny.

Microsoft decided not to offer any remedies to the CMA, leading to the phase 2 investigation. As Ars Technica notes, it could result in the merger being prohibited or a requirement to sell some parts of the business. The CMA today released the full text (PDF) of its decision, which has prompted a biting response from Microsoft in which it claims the regulator is relying "on self-serving statements by Sony" and has adopted its rival's complaints without the "appropriate level of critical review."

Sony's biggest issue with the Microsoft deal is Call of Duty's future. The Redmond firm says Sony is significantly exaggerating the series' importance, and losing a single franchise would not challenge the Japanese giant's dominance. It adds that making Call of Duty available on its Game Pass service doesn't guarantee it will sell more Xbox consoles. Xbox head Phil Spencer previously confirmed that Activision Blizzard games like Call of Duty, Overwatch, and Diablo would end up on Game Pass if the deal completes.

"While Sony may not welcome increased competition, it has the ability to adapt and compete. Gamers will ultimately benefit from this increased competition and choice," Microsoft said in its response. Sony says the deal is "bad for competition, bad for the gaming industry and bad for gamers themselves."

Microsoft had to defend the Activision Blizzard deal after Sony raised concerns over CoD in the past. The Windows maker promised that the next three games in the series, which includes CoD: Modern Warfare II, would be released on PlayStation, at which point Activision's contract with Sony ends. PlayStation CEO Jim Ryan called this proposal "inadequate on many levels."

As Microsoft must still appease regulators in other parts of the world in addition to the UK, Game Pass subscribers hoping to see CoD as part of their subscription might want to wait a while before getting too excited.