The Orange and T-Mobile merger has expanded its network into Amersham, Bolton, Chelmsford, Hemel Hempstead, Southend-on-Sea, Stockport, Sunderland, Sutton Coldfield and Wolverhampton.
Bradford, Coventry, Doncaster, Dudley, Leicester, Luton, Newport, Reading, Rotherham, St Albans, Walsall, Watford and West Bromwich are expected to be next in line following promises made by EE in December last year.
EE is currently the only UK operator providing 4G services in Britain, with coverage now having reached 27 towns and cities. Around 45% of the country's population is said to live in a connected area.
"To be ahead of schedule and covering approximately 45% of the population within just 90 days of the launch is a great achievement for our network team," said EE CEO Olaf Swantee.
"We continue to bring superfast mobile to more and more people, whether they're using their devices outdoors or in their homes and offices, and to increase the speed and consistency of our 4G and 3G network across the UK."
Bidding is under way on an Ofcom auction to sell off additional 4G spectrum, with Britain's top four mobile service providers among the seven companies competing for a share.
More 4G networks are expected to spring up over the course of the year, which may lead to a more competitive pricing structure for the costly data service.