4G mobile speeds halve in a year OpenSignal said the main reason for the slowdown is an increase in 4G mobile users. The networks are constantly rolling out improvements and working to increase capacity by adding more 4G masts, but this has failed to prevent congestion. The report also uncovered big differences in coverage and speeds for all of the major mobile networks across the country. Coverage is best in London, with users having access to 3G over 85 per cent of the time and to 4G over 50 per cent of the time. The south east and west midlands also comparatively well served. Wales has the worst coverage, with most parts of the country having access to 3G between 60 and 65 per cent of the time and to 4G less that 10 per cent of the time. "We've looked at consumers' real-life experiences and found big differences in service between mobile phone providers, depending on where you live or work," said Which? executive director, Richard Lloyd. We're calling on providers to publish the reliability and speeds their networks actually achieve so people can make an informed choice before signing on the dotted line. How would you rate your mobile service out of 5? EE is the best mobile network for coverage - ahead of O2, Vodafone and Three - according to the report. However, Vodafone users enjoy the fastest 4G speeds. Three is the best network for 3G in terms of bother coverage and speed, but OpenSignal points out that Three has no 2G network, so if a user has no 3G or 4G connection they will be unable to make calls or texts. Commenting on the report, EE admitted that mobile data networks can slow down when more people use them, but said that that the report is "flawed in many ways, not least as it muddles coverage with time spent on the network." "We have not seen any reduction in our own speeds, and would question the way that Which? is measuring these," an EE spokesperson said. If we look at Speedtest.net's tens of thousands of results from the same period, it tells a very different story. Samuel Johnston, head of marketing at OpenSignal, said: "We hope this report can draw better attention to the current state of mobile network coverage in the UK, and help consumers better understand how the networks differ in terms of speed and real-world coverage."