The consumer group’s analysis of data from UK cashpoint network Link found that residents in almost one in eight rural communities, 153 postcode areas in total, that have lost their last free-to-use ATM face travelling at least one kilometre to their next one.
Some people may face travelling significant journeys by car, bus or even ferry to find a free-to-use ATM.
Which? said some cash machines have closed despite being given “protected” status by Link – in recognition of their critical importance to local people and businesses.
It said that overall, 194 “protected machines” closed between January 2018 and July this year.
A statement from Link said: “Link will ensure that all ATMs in remote communities are protected and replaced if necessary unless there is a post office nearby.
“The protected areas highlighted by Which? have post offices and so Link does not intend to subsidise competing ATMs in these areas.”
But Which? said its research found that some areas did not have a post office handy and some branches had restricted opening hours.
It argued that while post office branches can provide a “valuable back-up or alternative to an ATM”, they are not a direct substitute for a cashpoint.
Which? said many rural areas also suffer with patchy broadband and mobile services - making it difficult for some people and businesses to switch to online banking and digital payments as a reliable alternative when convenient access to cash is cut.
Among the communities in Which?’s analysis, Gargunnock in Scotland lost its high street cashpoint, and residents face travelling more than nine kilometres to find another free option.
And a ferry ride or 40-minute car journey is now required for the people of Tighnabruaich in Scotland to access a free machine, which is 37km away.
Link recently announced an initiative to provide cashpoints to under-resourced areas.
Which? said it believes that legislation is needed to guarantee that consumers can continue to access and pay with cash for as long as it is needed.
Jenny Ross, Which? money editor, said: “A lack of proper oversight has seen thousands of cash machines and bank branches around the country closing - leaving whole communities cut off from the cash local people and businesses desperately need.”
Federation of Small Businesses national chairman Mike Cherry, said: “Cash deserts threaten to create small business deserts.”