MPs have urged the Royal Bank of Scotland and Lloyds to remove restrictions on customers with basic bank accounts using cash machines run by other banks.

The Treasury Select Committee said restricting access to cash machines could compromise the network and affect the most vulnerable people in society.

Barclays, HSBC and Santander have all pledged to continue to provide basic bank account holders with unrestricted access to cash machines, but now MPs will ask other providers to do so.

About 8.4 million basic bank accounts are used by people who do not necessarily meet banks' minimum criteria to open a personal current account, possibly due to a poor credit history. They often do not offer a debit card or an overdraft, but access to

such accounts can help lower-income households to manage their money and access other finance products.

RBS and Lloyds currently limit access to cash machines for their basic account holders, with different restrictions applying to basic accounts with Lloyds TSB, Halifax and Bank of Scotland arms of Lloyds Banking Group.

RBS last year said bank account customers would no longer be able to use cash machines run by other banks or independent third parties.

Some similar restrictions apply to customers with a Lloyds TSB basic bank accounts.

Andrew Tyrie, chairman of the Treasury Select Committee, said: "The committee understands the need for banks to control costs, particularly in these difficult times.

"In this instance, the financial benefits to Lloyds and RBS appear relatively small but those affected would be among the most vulnerable people in society."

Meanwhile, banks, building societies and credit unions must have stickers or posters in branch windows publicising the compensation scheme, along with a sticker at the cashier's window or desk, a poster in a highly visible position inside and information on their websites, according to the Financial Services Compensation Scheme.