Large numbers of properties in North Devon and Torridge are being left without adequate 4G coverage, according to Ofcom.
More than two thirds of homes and businesses in Torridge do not have full 4G coverage, and more than half in North Devon do not either.
Figures from the communication regulator’s Connected Nations report revealed 69 per cent of premises in Torridge did not have reliable 4G coverage from all four mobile phone networks.
The figure is slightly better in North Devon, although 57 per cent of premises in the area were without reliable coverage.
Coverage in both areas has improved over 12 months. In 2017, 81 per cent of North Devon premises were inadequately covered, compared to 79 per cent in Torridge.
Campaigners have said that it is essential for consumers to get access to 4G from all four networks, so they do not have to suffer localised monopolies.
The County Land and Business Association is calling on the Government to introduce legally binding targets to force the mobile phone networks to extend 4G coverage.
It said that mobile phone operators were letting rural areas become ‘a digital wilderness’.
CLA senior economic adviser, Dr Charles Trotman, said the association’s aim is to push for comprehensive and reliable coverage from all four major networks – EE, Vodafone, Three and O2
He added: “Our objective is universal coverage, but everything is predicated on the operators themselves to put the infrastructure in place.
“We need to incentivise all operators to branch out, to give consumers more market choice and avoid localised monopolies.”
Ofcom has proposed introducing obligations that require networks to deliver better quality indoor coverage.
An Ofcom spokesman said: “We agree mobile coverage must improve, particularly in rural communities, and we’re working with the Government and the industry to support this.
“We want mobile companies to extend their networks as a priority, and we’ve announced plans to make them increase coverage for rural areas as we release more airwaves next year.”
Ofcom’s report also measures coverage by geographical area, for someone using their phone outside.
The figures show that 45 per cent of the total area of Torridge is covered by all four 4G networks, while 48 per cent of North Devon is covered.
A spokesman for the Department for Digital, Culture, Media and Sport said: “We have implemented major changes to planning laws and made it cheaper and easier for the industry to roll out masts.
“But the mobile companies now need to act fast on these reforms and deliver better coverage across the UK, particularly in rural areas.”