An MP has increased the pressure on two banking groups to reverse their decision to limit access to cash machines for some vulnerable customers.
Andrew Tyrie, who chairs the Treasury Committee, has called on Lloyds and RBS to reconsider moves to restrict access for basic bank account customers.
Basic accounts, often opened by those with a chequered credit history, do not offer overdrafts or cheque books.
The banks have blamed high costs for the use of other banks' ATMs.
In August, one million RBS customers with basic bank accounts were told they could withdraw money only from RBS, NatWest, Tesco or Morrison cash machines.
In a letter to Mr Tyrie, the bank's head of retail banking, Brian Hartzer, said that these accounts were being run at a loss, which needed to be reduced. A charge was made each time a customer checked their balance or withdrew money from an ATM run by another company so these costs needed to be cut.
Lloyds Banking Group made the same argument, pointing out that the charge was 21p per transaction at branch ATMs, and rising to 35p per transaction at prime site cash machines, such as mainline railway stations.
It has 4.3 million basic bank account holders across the Lloyds TSB, Bank of Scotland and Halifax brands.
RBS and Lloyds are the two high street banks with significant taxpayer shareholdings.
Mr Tyrie said: "I understand the need to reduce costs, particularly at this difficult time.
"However, the decision to restrict access to cash machines has major implications for universal banking services and appears to target those vulnerable consumers who are most at risk of financial exclusion.
"Not every bank is restricting access. This issue would benefit from further consideration."