Almost two thirds of the UK's bank branches have shut over the last three decades, research indicates.
The scale of closures has sparked warnings that millions of people are struggling to access vital financial services and cash that they need.
Official records show that in 1988 banks and building societies had 20,583 branches, but analysis by the consumer group Which? suggest this number has plummeted to just 7,586 branches now.
It means a fifth of people now live nearly two miles from their nearest branch, while almost one in 10 have to travel more than three miles.
Although people can access their high street bank accounts at the Post Office, a survey of more than 2,000 people found many people are unaware they can use the network for everyday banking services.
Which? also points out not all the services offered by banks are currently offered by the Post Office, and that customers still need to call into a local branch for some transactions.
The consumer group said that with many communities faced with the double whammy of bank and cash machine closures, action is needed to ensure people are not financially excluded.
Ceri Stanaway, Which? money editor, said: "The true scale of bank branch closures in recent decades is staggering - and has left millions of people struggling to access the vital financial services and cash that they need.
"For many there is simply no substitute for a dedicated branch and the wide range of services it offers and many customers now face having to travel long distances if they are to avoid financial exclusion.
"We want to see banks properly justifying the reasons for closure and taking into account their customers' needs before shutting their doors - and their customers out."
A spokesman for trade association UK Finance said: "Bank branches play an important role in the life of local communities and decisions to close them are never taken lightly.
"Consumers are increasingly choosing newer ways to help them with their banking, using technology to check balances and make payments - or even speak to your bank 24/7.
"But technology is not for everyone, so the major banks have made arrangements for customers and businesses to do their day-to-day banking at over 11,500 Post Office branches nationwide.
"Banks are also investing in new ATMs and mobile bank branches to reach more rural communities, and the industry's access to banking standard supports business and communities, helping them to access alternative ways to bank when a local branch closes.