Both Vodafone and Three said they "remain confident" in being able to push through the deal after the CMA voiced concerns that the merger of the two of the UK's largest mobile operators could potentially lead to price hikes for millions of mobile customers and a potential reduction in service offerings.

In an effort to push the deal through, Vodafone and Three pledged on Monday to freeze tariffs at £10 or below for value-focused customers, and to maintain social tariffs on both the SMARTY and VOXI 4 Now brands. The pair also proposed an offer to encourage mobile virtual network operators, such as Giffgaff, to use their potentially increased network capacity.

Separately, Vodafone also confirmed that shareholder approval would not be required, due to changes in the UK Listing Rules in July, meaning the deal's future lies with the CMA, which must make a decision by 7 December.

Reporting by Iain Gilbert at Sharecast.com