The CMA's decision comes after it opened an antitrust probe in to the deal in January and announced an in-depth investigation in April. Last month, the competition watchdog laid out a path for the deal to move forward, if certain remedies were adopted.
The regulator was concerned that the merger, which will trim the number of major telecommunications network players from four to three, would lead to higher prices or reduced services.
Vodafone said the deal is expected to be formally completed in the first half of 2025.