Banks could be forced to admit to the number of complaints received from customers under proposals from the City watchdog.
The Financial Services Authority (FSA) wants to name and shame firms that have frustrated customers by publishing lists on the most complained about products every six months in a move to increase transparency.
It said consumers should also be able to find out how many complaints a firm has opened and closed, the number that were resolved within eight weeks and the percentage of complaints that were upheld.
Banks and building societies will have to provide the data every six months, which will be collated and published by the FSA.
The FSA will not require firms to publish the details of complaints that have been