The worst offender was Bank of Scotland which received 884 new complaints related to mortgages and home finance between July and December 2011.
Santander received 515 new mortgage complaints, followed by Barclays with 458 mortgage complaints and Northern Rock with 330.
During the six-month period, the ombudsman service received a total of 106,193 new complaints relating to individual financial businesses including banks, insurance companies and investment firms.
Some 89% of the total number of cases involved 163 financial businesses out of more than 100,000 businesses covered by the ombudsman.
Of the data published, 46,700 cases related to payment protection insurance – a decrease of 53% on the 98,632 PPI cases received in the first half of 2011.
The Ombudsman said this reflects the impact of the Financial Services Authority’s special arrangements allowing banks more time to deal with their backlogs of cases following their unsuccessful legal challenge on PPI complaint handling.
The ombudsman service is expecting to receive a record 165,000 PPI complaints in 2012/2013.
In the second half of 2011 the ombudsman service upheld an average of 72% of complaints in favour of consumers, compared to 47% in the first half of 2011 – reflecting the impact of PPI cases.
Across the 163 individual businesses included in the complaints data, the overall uphold rates varied substantially between 6% and 98% upheld in favour of consumers.
or PPI cases specifically, uphold rates ranged between 6% and 100%.
Natalie Ceeney, chief executive and chief ombudsman, said: “The proportion of complaints that we have upheld in favour of the consumer – ranging from 6% to 100% – clearly highlights the difference in PPI complaints handling across major businesses over this period.
“It also reflects the efforts made by some businesses to resolve quickly the hundreds of thousands of PPI complaints that had built up during the banks’ unsuccessful PPI legal challenge.
“We now hope to see all businesses who were involved in PPI mis-selling resolving their customer’s complaints fairly, properly and quickly.”
Which? chief executive, Peter Vicary-Smith, added: “Today's data from the Financial Ombudsman Service is further evidence that some banks are systematically failing to treat their customers fairly when things go wrong.
“It is especially unacceptable that tens of thousands of consumers have been forced to take their PPI compensation claim to the ombudsman, where the overwhelming majority of complaints are then upheld.
"This is exactly why we need the Financial Services Bill to create a strong, open and proactive watchdog which not only makes sure that people get proper redress when products are mis-sold, but that would ban dodgy financial products before they cause problems.
“In the meantime, the Financial Services Authority must take enforcement action against any banks which continue to drag their feet on settling complaints."
