The UK's Competition and Markets Authority (CMA) has confirmed it will launch, as expected, a Phase 2 investigation into the proposed merger of Vodafone and Three.

CMA said in a statement that the Phase 2 investigation into the deal will run from now until September 18, 2024.

"The CMA has referred the anticipated joint venture between Vodafone Group Plc and CK Hutchison Holdings Limited concerning Vodafone Limited and Hutchison 3G UK Limited for an in-depth investigation, on the basis that, on the information currently available to it, it is or may be the case that this merger may be expected to result in a substantial lessening of competition within a market or markets in the United Kingdom," said the CMA today.

Last month, the regulator voiced concerns that the merger will lessen competition in the UK telco market, following a 40-day review into the £15 billion ($18.5bn) merger, set to create the UK's biggest telco with more than 27 million customers.

If the deal, which was first announced in October 2022, is given the go-ahead, it will consolidate the UK telco carrier market from four to three, giving consumers less choice, argues the CMA.

The merger will give Vodafone a 51 percent majority stake in the combined entity, currently labeled as "MergeCo," with CK Hutchison's Three holding the remaining 49 percent.

Both telcos have previously welcomed a more in-depth probe into the proposed union.

“This was an expected next step in the process and is in line with the timeframe for completion that we set out from the outset,” said the two telcos in a joint statement today.

“Vodafone UK and Three UK remain confident that the transaction will drive stronger competition in the mobile sector and give customers and businesses a step-change in network quality, speed, and coverage from day one."