A third of complaints against the major UK insurers were found in favour of the consumer, half the number upheld against banks, figures from the financial ombudsman (FOS) show.
According to data for the first six months of 2009, upheld complaints against the likes of Aviva, Axa, L&G and Friends Provident fell around the 30% mark.
Axa Insurance received the most complaints (513), according to the FOS, which is today naming and shaming the worst complaints offenders for the first time.
Four in ten of these cases were found in favour of the consumer but Phoenix Life, the next biggest complaint recipient, was deemed not to have a case to answer on two-thirds of complaints.
The FOS upheld 49% of the 164 complaints it received about Windsor Life, but only 27% of 254 cases were upheld against Scottish Widows.
Elsewhere, 31% of cases against L&G Assurance and Friends Provident Life & Pensions were upheld.
Not only did banks receive the vast majority of the complaints, but the percentage of upheld cases was also high.
In the case of Capital One Bank, 91% of 1,744 complaints were upheld, while 81% of almost 7,000 complaints against Lloyds TSB Bank were found in favour of the consumer.
Lloyds and its subsidiaries accounted for more than 15,233 complaints, more than a fifth of the total received by the FOS.
Seven in ten complaints were upheld against Barclays and The Royal Bank of Scotland, while figures of 67%, 66% and 63% relate to Abbey National, Alliance & Leicester and MBNA Europe. Six out of ten cases were upheld against NatWest and HSBC.
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