It sounds great, doesn’t it? Transfer your outstanding credit card balance to another card and get charged 0% interest for three, six, nine, 12 months – sometimes longer. Must be a no-brainer; who wouldn’t do it? Why wouldn’t you do it?

Well, Banks love you to do it. They made £240 from credit cards offering 0% interest rates on transferred balances in Britain in the last twelve months.

They made the money from transfer fees.

Many people who moved their balance from one company’s credit card to another’s to save money on their interest payments did not know that they would have to pay up to 3% of the balance to make the switch. If you moved a balance of £5,000 you would have to pay £150; if you transferred £3,000 it would cost you £90.

The Office of Fair Trading (OFT) is considering looking into these fees, just a few days after it began a High Court action against banks with regard to charges for overdrafts.

Balance transfer deals at 0% interest have been used by some customers (so called “rate tarts”) to move their credit card balances around to manage their debts and avoid interest charges for as long as possible. At the moment there are some 150 cards with 0% interest on balance transfers, but you’d be hard-pressed to find one that doesn’t now charge a transfer fee. There are some, but those there are, such as Norwich and Peterborough Building Society and Britannia Building Society, are available to members only.

The fees erupted in 2006 after the OFT had cracked down on penalty fees - reducing them to £12, sometimes from £30 – and Banks had to find other ways to bolster their huge profits.

In the year to the end of June more than £239m was paid to banks and building societies in balance transfer fees. Nearly 12 million people have switched cards in that time, and the average fee has been a shade under £20.

The British Bankers' Association said the fees covered the transfer of direct debits and the checking of credit histories. That does not really explain why the charge would be higher for anyone transferring a bigger balance.