Lloyds TSB Bank has topped the Financial Ombudsman Service’s (FOS) list of complaints for the first six months of the year.

The group had a total of 12,750 new complaints, with 8,474 being insurance-related.

It almost attracted twice as many complaints as any other regulated firm.

The data published today on the ombudsman’s website covers consumer complaints handled by the ombudsman service between 1 January and 30 June 2010. The data includes both the number of complaints received about individual businesses and the percentage of complaints upheld by the ombudsman service in favour of consumers.

During this six-month period, the ombudsman service received a total of 84,212 new complaints – a small increase on the 82,136 cases received in the second half of 2009. Of these new cases, 89% related to 160 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 30 to 12,750. Five financial services groups continued to have more than 3,000 complaints each, which together accounted for 47,507 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 size of the business. 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].