Nationwide Building Society revealed last week that it has been approached by a fee-charging cash machine operator trying to buy its network of remote ATMs.

The announcement highlights the extent of the change currently underway in the industry, as the number of fee-charging cash machines continues to rise.

In December, Nationwide issued a report saying that consumers are now paying £140m a year in ATM charges, 133 per cent up from the year before.

At a Treasury Select Committee hearing this month, HBOS chief executive James Crosby told MPs that half of all cash machines are likely to charge a fee in the future, as they generated more revenues for ATM site owners.

At the same hearing, RBS chief executive Benny Higgins said the fact that the switch to fee-charging ATMs would continue.

Banks have been closely watching consumer reactions to the rise in fee-charging cash machines, as selling off their remote ATM estates to operators like Cardpoint or Moneybox represents an opportunity to cut costs.

Most High Street banks currently outsource the management and maintenance of their cash machine networks to third party IT services firms, a cost they would love to clear from their bottom lines.

In May, independent cash machine operator Cardpoint paid HBOS £75m for 816 of its cash machines - demonstrating the payoff six months later when it reported a 203 per cent increase in revenue.

The operator charges customers anything up to £1.75 per transaction in return for providing cash machines in more remote locations, such as petrol stations, currently dispenses more than £300m every month.

But Cardpoint chief executive Mark Mills argues that the growth in fee-charging ATMs has been purely consumer led.

'The vast majority of our customers repeat-use our service week in week out,' he told the committee.

Nationwide executive director Stuart Bernau warns that the growth in free ATMs is stagnant, and challenged the assumption that even though the number of fee-paying machines is rising, the volume of paid-for transactions is not.

'The suggestion that only five per cent of cash machine transactions will ever incur a fee is a misconception,' said Bernau. 'Experience from the US illustrates that it could go much higher.'