More than one million consumer complaints have been made about payment protection insurance to the financial ombudsman and up to 10,000 new cases are still being taken on each week.
Seven out of 10 (70%) of PPI-related complaints have been upheld in consumers' favour this year so far, up from just under two-thirds (65%) during the last financial year.
The Financial Ombudsman Service said two-thirds of the PPI complaints it has dealt with have been referred to it just in the last 18 months and i t is still taking on between 8,000 and 10,000 new PPI cases a week, mostly revolving around allegations that policies were mis-sold.
But its latest figures also suggest that the PPI mis-selling scandal has started to turn a corner and complaints are gradually drifting downwards, echoing some findings recently published by regulator the Financial Conduct Authority (FCA).
Chief ombudsman Natalie Ceeney said the financial sector appears to now be putting a stronger focus on consumers as the industry moves to repair "broken" trust.
While PPI still makes up around four-fifths (81%) of cases that the ombudsman deals with, the latest findings also show that PPI complaints have been edging down from a peak of over 145,000 cases received in the last three months of 2012.
A total of 247,399 PPI complaints were recorded by the ombudsman between April and September this year, made up of around 132,000 cases between April and June and 115,000 between July and September.
Ms Ceeney said: "Over the past year I've been hearing an increasing commitment to treating customers well - and restoring trust. It's great to hear that.
"But although financial services providers might have moved on - and are thinking about new products, better sales approaches and clearer pricing - I don't think customers have."
She said the relationship between banks and their customers is "like any relationship where trust has been broken".
Ms Ceeney added: "It can take a long time to forget what's happened, move on and be willing to accept promises at face value."
Consumers can turn to the ombudsman service for help when they have made a complaint to a financial services firm but are not happy with the outcome.
PPI is the most complained-about financial product that the ombudsman service has ever seen and it has previously complained that banks have been dragging their heels and not clearing up genuine grievances quickly enough. The ombudsman has recruited 2,000 extra staff over the last two years to cope with the scale of the scandal.
More than £18 billion has been put aside by firms to compensate customers who were sold PPI they did not want or need, amounting to around double the cost of the London 2012 Olympic Games.
Complaints figures released by the FCA last week showed that the number of PPI complaints made directly by consumers to financial firms dropped by almost one fifth in the first half of this year compared with the previous six months.
Just under 1.8 million new PPI cases were recorded in the first half of 2013 by the FCA, which regularly publishes firms' complaint figures to encourage them to improve the services they provide.
Before the FCA's latest figures, complaints made to financial firms had been steadily rising since around 2010.