Some 70% of UK businesses experience problems with mobile coverage in parts of their local area, according to research by the British Chambers of Commerce (BCC).
It reveals that 29% of companies have unreliable mobile internet connections, with this number rising to 54% in rural areas, while only 42% of firms have a 4G connection.
The findings show that these problems exist all across the UK, including in the City of London, denying businesses basic requirements for companies to work on the move, trade online, and connect with customers and suppliers.
"It's clear that the UK is lagging in the delivery of access to a world-class digital infrastructure" BCC director general, Dr Adam Marshall, said. "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.
"The Chamber Network’s election manifesto specifically calls for these issues to be rectified, and for the next government to provide all businesses with super-fast and reliable broadband and mobile connectivity to boost confidence and productivity."
The research involved a survey of 1,465 business in January, 78% of which operate in the services sector, in order to understand how firms rate the overall reliability of their broadband connections.
It was found that 6% of companies typically obtain a 2G connection, and 25% a 3G one, while 57% of businesses with more than 500 employees have 4G connections, compared with 41% of firms with less than five staff.
There are now calls for the government to make policy changes that allow for better internet coverage, and for the UK's broadband regulator to intervene.
"Some of the solutions are obvious," Marshall continued. "Relaxing planning laws to allow for taller masts would be a quick win for the next government to help improve mobile coverage.
"As the regulator, Ofcom must do more to hold providers to account for the services advertised to business customers, and put in place remedies 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.