Albania and Peru have better mobile phone coverage than the UK, according to a report from the National Infrastructure Commission (NIC).
The report, which said there are "too many digital deserts" across the country, ranked Britain 54th in the world for 4G coverage as people can access it just 53% of the time.
The figures have prompted the NIC to call on the Government to introduce a new universal service obligation to ensure that text, talk and data are available wherever needed.
In a statement, it said the Government "must now play an active role to ensure that basic services are available wherever we live, work and travel, and our roads, railways and city centres must be made 5G ready as quickly as possible".
The successor mobile network standard to 4G is 5G, which will offer much greater speeds, although its technical details are still being worked out.
5G will be used to enable communication between many more devices, from cars to trains to streetlamps and traffic lights, as part of the so-called "internet of things".
A resilient network would be important for the development of driverless cars, for example, which will need to be in constant communication with networks.
The NIC report calls for the Government to build networks alongside key rail routes and motorways by 2025.
NIC chairman Lord Adonis said: "5G is the future - ultra-fast, and ultra-reliable it has the potential to change our lives and our economy in ways we cannot even imagine today.
"But the UK is currently languishing in the digital slow lane. 5G offers us a chance to start again and get ahead.
"If Government acts now we can ensure our major transport networks and urban centres are 5G ready in time to give British industry every chance to lead the world in exploiting its applications."
Chi Onwurah, Labour Shadow Minister for Industrial Strategy, Science and Innovation, called on the Government "to take responsibility for developing the digital infrastructure that will equip our economy for the future".
She said: "Improving our digital connectivity will be a huge boon for business, and enable the UK to play a leading role in the coming 4th Technological Revolution.
"After a series of connectivity setbacks, the Government is now unable to offer anything but tinkering at the edges and have missed their own connectivity targets."
- Sky News