EE, the UK's biggest mobile operator, said it is on track to sign up 14 million 4G customers by the end of the year.

The group, which has 548 stores, added 1.7 million 4G accounts in its first three months of the year to March 31, giving it 9.3 million customers, a more than two-fold jump on a year ago.

However, the group said its operating revenue, which included the impact of regulatory cuts, fell 1.1% to £1.5 billion.

In February, UK rival BT agreed a £12.5 billion takeover of EE, taking control from its current owners Deutsche Telekom and Orange. They will hold stakes of 12% and 4% respectively in BT.

The deal raises hopes of cheaper deals for customers as the merger will enable BT to sell its fixed telephone, broadband and TV services to EE's customers, and accelerate its plans to offer seamless convergence between fixed Wi-Fi and high-speed fibre networks with mobile 4G technology.

The moves comes at a time of great change in the industry as Three owner Hutchison Whampoa agreed buy rival O2 for £10 billion in March from Spain's Telefonica, while Sky has announced plans for its own mobile offering using O2's network.

During the period EE, which has 30 million customers in total, announced a £1.5 billion three-year investment programme which aims to boost its 4G coverage to 99% of the population by 2017.

It added that its 4G coverage currently reaches 87% of the UK population, over 55 million people, making it the largest provider in Europe.

EE chief financial officer Neal Milsom said: "We are delivering strong, consistent commercial performance by giving our customers the best mobile voice and data network experience in the UK."

He added that as much of the UK market now has a smartphone it was "leading the charge" into cross-selling a range of 4G products and services across tablets, TV, wifi and fixed broadband to its existing customers.

However, brokers at Jefferies noted: "Mobile service revenues continue to decline in spite of strong 4G adoption."

The firm added that during the period it completed the hiring 1,000 more call centre staff in the UK in a bid to improve customer service.

BT's acquisition of EE marks its re-entry into the mobile phone market for the first time since spinning off its BT Cellnet operation in 2001. It hopes to complete the deal by the end of the summer should regulators give the move the all-clear.