The Competition and Markets Authority (CMA) is now supporting the merger between Vodafone and Three's UK mobile operations.
The CMA believes that long-term competition will be boosted if the companies fulfill their promises to invest in their combined network.
Ofcom will have powers to force Vodafone and Three to upgrade their network over the next eight years and the companies must keep certain mobile tariffs and data plans in place for three years.
The CMA's decision takes into account the poor state of 5G performance in the UK and the lack of cut-throat competition in the current four-way market.