Lloyds, Royal Bank of Scotland and NatWest have announced that they will bar any basic bank customers from using rival banks' ATMs.
The move means those account holders, who are usually the poorest customers and not in a position to pay for fancier accounts, won't be able to use 80% of Britain's cashpoints.
RBS has defended its decision by saying that basic accounts are free to customers but if they use rival cash machines RBS incurs a charge – estimated at 50p – 75p per cash withdrawal.
"It is unsustainable for us to offer free access to other banks' ATMs for basic accounts as we face a charge per bank transaction, which needs to be recovered elsewhere," says a spokesperson for the bank.
In the coming months customers will be informed if they are affected by the change, which will mean they can only use RBS and NatWest ATMs along with some supermarket cash machines.
Lloyds basic account customers will be in an even worse position as they will be limited to only using Lloyds machines, and they won't even be able to withdraw money from Halifax or Bank of Scotland which are both owned by Lloyds.
"This change will increase financial exclusion as it leaves basic bank account holders at RBS unable to access around 80% of the free cash machines in the UK," says Dominic Lindley of Which?.
"These account holders will be inconvenienced and might incur extra costs when travelling to find a cash machine they can use," he adds.