The findings were revealed in the latest FOS newsletter, published on its website.
Claims-management companies were most rife in the PPI scandal, 76 per cent of the cases brought by them to FOS related to PPI.
These include “cold calling” potential clients and “no win, no fee” offers.
FOS says that consumers turned to claims-management companies as they felt intimidated at bringing a complaint against a large financial institution.
Speaking at the British Bankers’ Association conference yesterday, FOS chief executive Natalie Ceeney, said: “We know that some claim-management companies fail to check even the most basic of facts, such as whether the product complained about was bought.
“But we also know that many consumers don’t feel they have time or ability to bring a complaint themselves. They feel overwhelmed and intimidated by large financial institutions and lack the resilience to battle through banks’ complaints processes.”
She said the banks needed to give consumers confidence that they wouldn’t be fobbed off.
Barclays recently ran a campaign with Which? to persuade consumers to refer complaints direct to Barclays and other organisations have made their complaints web pages simpler and easily accessible.
Ms Ceeney said: “Increased consumer confidence in a bank’s own complaints process will surely mean less demand for claims-management companies.”
• Want to receive a free weekly summary of the best news stories from our website? Just go to home page and submit your name and email address. If you are already logged in you will need to log out to see the e-newsletter sign up. You can then log in again.