The FCA has asked firms to review 2.5 million payment protection insurance complaints which may have been unfairly rejected or where consumers may have been paid too little in redress.
Since the regulator started tracking payments in January 2011, £16bn has been paid out in compensation.
The FCA says firms are now improving how they deal with complaints. But it has asked banks, credit card providers and personal loan firms to go back over 2.5 million old complaints from 2012 and 2013 where consumers may not have been fairly treated.
Although 13 million PPI complaints have been brought since 2007, firms are now writing to a further five milllion customers who are at high risk of having been missold PPI but have not yet complained.
FCA chief executive Martin Wheatley says: “Making sure anybody previously missold PPI is treated fairly now, and paid redress where it is due, is an important step in rebuilding trust in financial institutions. In around 2.5 million complaints this was not necessarily the case so, at our request, firms will be looking at these complaints again.”
The Financial Ombudsman Service has received over one million complaints from people unhappy with the response from their provider, about a quarter of all rejected complaints.
Where complaints have been taken to the FOS, seven out of 10 decisions were upheld.