Banks received 2.18m complaints from July to December 2014, a fall of 14 per cent on the same period of 2013.
Of those, 1.06m were still PPI complaints – making up 48.6 per cent of the total.
This is the first time PPI mis-selling has accounted for less than half of all complaints in more than three years.
However, insurance compensation payments still made up the vast majority of all redress paid to customers over the six-month period – amounting to £2.15bn of the total £2.44bn dished out by the sector.
Meanwhile, complaints about other finance products increased. Non-PPI complaints increased two per cent on the year to 1.12m.
Banking and credit cards saw the biggest increase, with complaint volumes rising six per cent to 605,799.
That category also saw the biggest amount of compensation paid to mistreated consumers, following PPI, at £144.7m, more than double the £58.3m in the same six-month period of 2013.
“While the overall decreases we have seen should be welcomed there is still more for financial services firms to do,” said the watchdog’s Christopher Woolard. “The FCA’s challenge to those firms is to put the necessary measures in place to ensure we see a consistent fall across all sectors.”
By bank brand, the worst offender is Barclays, with 276,626 complaints, which is down one per cent on the previous six-month period.
Next is Lloyds Bank, with 242,782 – down eight per cent.
Bank of Scotland – also part of the wider Lloyds Banking Group – is third with 231,869, a drop of 13 per cent.