Bank customers have been warned by financial information firm Moneyfacts that they may soon face stricter charges on unauthorised overdrafts.
Overdraft charges could rise despite an OFT investigation
Lloyds TSB has announced that from 1 November it will no longer give customers a £10 "buffer" if they accidentally slip into the red.
Moneyfacts said that other banks may adopt a stricter attitude as well.
The firm suggested this was a response to the squeeze on credit card charges by the Office of fair Trading (OFT).
This year the OFT forced banks to cut the charges they levy on customers who do not pay their credit card bills on time to £12.
It is now looking at the charges imposed on overdrafts, suggesting that these are too high as well.
Despite this, seven banks this year have raised their authorised overdraft rates by up to 2%.
"With the OFT challenging credit card charges it looks as if the banks are looking to recover some money from personal current account holders," said Lisa Taylor of Moneyfacts.
The tariff structure that banks have devised for charging customers with unauthorised overdrafts are very complex and vary widely from one bank to another.
Typically they involve a combination of a buffer zone - for example, £100 - but with one-off fees and much higher interest rates being charged if that zone is exceeded.
As a result, someone accidentally going into the red, without authority, for just one day will soon be charged a fee of £30 and interest of 29.8% by Lloyds TSB, once its buffer zone is abolished.
At the other end of the scale, a £1 unauthorised overdraft at the Alliance & Leicester currently incurs neither a fee nor any interest, as its £5 buffer zone is free of both a fee and interest.
Ms Taylor said: "While current account fees look excessive, the problem is made worse by the lack of transparency caused by complex terms, conditions, waivers and by every provider charging in a slightly different way."
The OFT started its six-month probe into current account charges, including those for unauthorised overdrafts, last month.