The British Chambers of Commerce (BCC) has urged Ofcom to do more to support business broadband customers.
According to a new BCC survey, 29 per cent of firms have unreliable mobile internet connections - with the figure standing at 54 per cent in the countryside.
Figures also showed that seven in ten firms experience mobile not-spots, areas without any mobile coverage, or partial not-spots, where there is some coverage but only from a few networks, in their location.
Again, this problem was found to be most common among rural firms, with 91 per cent citing such issues, compared with 56 per cent of those in inner cities.
Similarly, figures showed that while 54 per cent of inner city firms are likely to have 4G, the same is true of just 25 per cent of companies in rural areas.
The BCC has therefore called on telecoms regulator Ofcom to intervene and do more to hold broadband providers to account for the services advertised to business customers.
Dr Adam Marshall, Director General of the BCC, said the watchdog must implement measures that are "as strong for business users as they are for individual consumers".
"According to their rules, virtually all UK premises must receive 4G signal by the end of the year, but the results of our research suggest that we’re a long way off achieving that target," he commented.
Dr Marshall flagged up relaxing planning laws as one "obvious" solution, as this would allow for taller masts to be erected.
"It’s clear that the UK is lagging in the delivery of access to a world-class digital infrastructure," he continued.
"While there have been welcome announcements to roll out 5G in the future, it’s clear that getting all businesses access to 4G first remains a top priority."
Dr Marshall went on to insist that being able to use mobiles and access the internet are "basic requirements for companies to work on the move, trade online and connect with customers and suppliers".
However, he said many businesspeople have become frustrated by poor connectivity, both in rural and urban areas.
"'Not-spots' are prevalent across the UK," Dr Marshall added.
"It's incredible to hear that in this day and age, there are even places in the City of London where businesses can’t get reliable coverage."