A fifth of shoppers have been turned away when trying to pay with cash since lockdown rules eased.
A survey by Which?, the consumer group, found that 18pc of consumers had been unable to pay with cash at least once when trying to buy something between April and July.
Of those who had their cash payment refused, one in six were then unable to complete their purchase.
This comes despite some eight in 10 consumers thinking businesses and shops should continue to accept cash.
Telegraph Money’s Keep Cash campaign recently secured commitments from more than 20 high street retailers to continue accepting physical currency. More than 50 politicians from across the political spectrum have also backed this newspaper’s campaign.
Cash usage and acceptance is particularly relied upon by the vulnerable and the elderly. Around eight million adults would struggle without cash, with 1.4 million people not having a bank account and relying on cash to survive, according to the Post Office.
Some 16pc of vulnerable adults rely on notes and coins, and dependency on physical money is highest among pensioners, according to the Financial Conduct Authority, the City watchdog.
Younger generations also rely on cash. A study by the FCA found that nearly a quarter of people aged 18 to 24 had struggled to cope with businesses shunning cash.
Natalie Ceeney of the Access to Cash Action Group, an industry group, said: “This is really worrying to see. Not everyone is able to use digital and contactless payments. What happens if people can’t buy food or medicine? We’ve all focused on the issues about getting cash – but the issues about being able to pay with cash are just as important.”
Which?’s Jenny Ross said: “Cash is still a vital way to pay for millions of consumers, so it’s very concerning to see many people still reporting difficulties when trying to spend their notes and coins, even as the country moves out of lockdown restrictions.
“The government must press ahead with plans for legislation to protect cash and should make the FCA responsible for tracking cash acceptance levels.”