Vodafone (VOD.L) has completed its £15 billion mega-merger with Three UK in a deal creating a “new force in UK mobile”.

The mobile phone giant said the merger of the UK network businesses officially completed on May 31, nearly two years after it was first announced.

VodafoneThree – now the biggest mobile phone network in the UK with around 27 million customers – pledged to invest £11 billion over the next 10 years to help boost its 5G capability, with £1.3 billion being spent this financial year, following the tie-up.

Margherita Della Valle, Vodafone group chief executive, said: “The merger will create a new force in UK mobile, transform the country’s digital infrastructure and propel the UK to the forefront of European connectivity.

“We are now eager to kick off our network build and rapidly bring customers greater coverage and superior network quality.

“The transaction completes the reshaping of Vodafone in Europe, and following this period of transition we are now well positioned for growth ahead.”

The companies first announced the landmark deal in June 2023 – in a major shake up of Britain’s mobile phone sector.

It was scrutinised closely by the Competition and Markets Authority (CMA) amid concerns it could substantially reduce options for mobile customers and lead to higher bills.

But the CMA gave the green light to the deal in December last year, with conditions.