The business received more than 400,000 complaints in the second half of last year, largely relating to the mis-selling of personal protection insurance (PPI).
However the combined complaints to Lloyds Banking Group – which owns both Lloyds TSB and Bank of Scotland – collectively topped 760,000.
The figures also reveal that the total amount of compensation paid out by the banking industry during the second half of 2012 was £2.95bn, a decrease from £3.17bn during the first half of the year.
Martin Wheatley, chief executive of the FCA, said publishing the figures was forcing institutions to act: “When I meet with the bosses of the financial institutions they frequently tell me that they don’t want to be at the top of the table, which means they strive to improve both their sales and complaints handling processes.
“Not only does our data help consumers compare and contrast their current bank or lender, but it also boosts competition among firms too.”
PPI complaints continue to drag down the industry’s profits and show no sign of abating, with 2.1m claims filed during the six month period. A thriving industry has grown up around the mis-selling scandal, dedicated to convincing members of the public to apply for compensation from their financial services provider.