Bank of Scotland saw the largest number of mortgage and home finance-related complaints during the second half of 2009, with 561 made to the Financial Ombudsman Service (FOS).

Its fellow Lloyds Banking Group business Lloyds TSB Bank had 4583 insurance-related complaints, again the highest in that field.

During this six-month period, the ombudsman service received a total of 82,136 new complaints – an increase of 18% on the 69,841 cases received in the first half of 2009. Of these new cases, 88% related to 155 financial businesses (out of more than 100,000 businesses covered by the ombudsman).

The number of new complaints about each of these individual businesses ranged from 31 to 9,952. Five financial services groups each continued to have more than 3,000 complaints each, which together accounted for 46,979 cases – over half of all the new complaints received by the ombudsman during this six-month period.

The number of new complaints against each business is likely to be affected by the business size. However, experts consulted by the ombudsman were unable to agree how size (or market share) should be taken into account, when comparing complaints statistics across the financial services sector [independent report on “contextualising”” complaints data opens as PDF].