The Financial Services Authority (FSA) is to publish details of the most frequently complained about banks and insurers.
It will only apply to firms that receive more than 500 complaints during a six-month period.
Sheila Nicoll at the FSA says, "We are committed to greater transparency where this will help consumers. For the first time, people will be able to see how many complaints particular firms receive and how they handle them."
Firms that receive 500 or more complaints in a six month period will have to publish the following information twice a year:
How many complaints they have opened and closed
The percentage closed within eight weeks
The percentage of complaints upheld
The firms will have to publish the information twice a year and will have to divide the information into banking, home finance, general insurance, pure protection insurance, life insurance, pensions and investment product areas.
The regulator will use the information to publish a list of complaints data covering all affected firms twice a year.
All affected firms will have published their first figures by 31 August 2010 and the regulator will publish the data in September 2010.