Nearly 20,000 complaints about Lloyds Bank were received by the Financial Ombudsman Service (FOS) in the first half of the year.
FOS data reveals that of the 19,569 complaints received, an astonishing 16,965 were to do with payment protection insurance (PPI).
In addition, Bank of Scotland, also part of the Lloyds Banking group, received 13,621 complaints via the FOS, with 9,945 concerning PPI.
Not far behind Lloyds in terms of overall complaints is Barclays, with 16,864, followed by Royal Bank of Scotland with13,391, HSBC with 10,072 and Santander with 6,434.
Santander: the bank people love to hate
However, despite the large number of complaints concerning Lloyds Bank, the number of complaints the FOS has managed to resolve in the consumers' favour is higher than with other banks.
Figures reveal that 63% of complaints were resolved with an outcome benefiting consumers, compared to 44% of Santander's, 43% of those from Barclays and just 20% of HSBC disputes.
PPI claims dominate the reasons for complaint: on top of the large number of PPI referrals for Lloyds, Barclays amassed a hefty 12,862 PPI referrals and RBS a sizable 8,644. Meanwhile, HSBC toted up 8,791 complaints and only resolved 18% in the consumers' favour.
How to reclaim your PPI premiums
According to Natalie Ceeney, chief executive of the FOS, these figures were recorded during a challenging period when many banks weren't co-operating fully with the FOS: "This period coincided with the time when most of the high street banks and some other financial businesses had put PPI complaints on hold because of their legal challenge against the FOS and the Financial Services Authority.
"As a result, complaints in this period about PPI were harder fought, and harder to resolve – particularly if we found in favour of a consumer."
In spite of this, consumer groups Which? and Consumer Focus argue that these figures indicate banks aren't addressing PPI claims sufficiently:
"If the next round of complaints data doesn't show a dramatic improvement then the FSA must take tough enforcement action against banks whose complaints handling isn't up to scratch," says Which? chief executive Richard Lloyd.
Oliver Morgans, financial services expert at Consumer Focus, says the figures are further proof of the banks' "inability to treat complaints fairly".
"There has been a massive surge in complaints about this issue with some banks showing a totally unacceptable uphold rate.
"Even the seemingly better performers appear to be unnecessarily stringing out complaints, challenging decisions and denying consumers compensation. All in all, the banks should be ashamed at their continued failure to tackle the PPI issue."
The FOS data covers complaints handled between 1 January 2011 to 30 June 2011.