Cardpoint said in it financial results statement yesterday that it was converting around a third of the 816 off-site machines it bought from HBOS to its fee-paying model, which charges customers between £1.50 and £1.75 for each transaction.

Laurence Baxter, senior policy adviser at Which?, says the news "confirms our worst suspicions that ATM charges are being gradually reintroduced through the back door and fear it may give other banks licence to follow suit".

Baxter says the move is further evidence that certain banks are shirking their social responsibilities of ensuring that all people have free and convenient access to their own money.

He adds: "This latest development increases the risk many of these new charging machines will be in places where basic and affordable banking services are most needed.

Which? has welcomed the Treasury Select Committee enquiry into cash machines that will investigate the fee-charging issue next month.

Recent research by Nationwide Building Society - which is campaigning for clearer labelling on fee-charging ATMs - found that the number of fee-charging ATMs in the UK has risen to 40% and now more than one in three machines charge consumers for making cash withdrawals.

A separate survey conducted by Marketing Sciences Limited on behalf of Nationwide found that - despite the introduction of stickers and on-screen messages on fee-charging machines - many people are still confused about ATM charges, which costs consumers £60 million a year.