As many as one in three complaints about insurance are being upheld by the Financial Ombudsman Service.
The ombudsman - essentially a free alternative to taking a financial services company to court - received 25,122 car, home and travel insurance complaints between April 2018 and March 2019.
That's 61% up on the number of complaints five years ago.
Just a third of these complaints were upheld by the ombudsman, on average, but success rates for some types of insurance, and some insurers, were much higher.
A complaint is categorised as 'upheld' when the ombudsman has ruled in favour of the customer, usually meaning the firm then has to pay compensation or reconsider a decision it's made.
Which? has looked at types of complaints most likely to be upheld, and the insurers most likely to be at fault.
We obtained the uphold rates, split by company level and type of insurance. Just over a third (35%) of buildings complaints were upheld. Of these providers, insurer Ocaso SA, Compania de Seguros y Reaseguros had the highest up hold rate - 43%.
The ombudsman upheld one complaint last year in favour of a couple whose subsidence claim had been declined. The insurer held the view that their property had been showing signs of damage indicating subsidence since they'd bought their property - which they'd failed to report.
The couple contended they'd answered all questions put to them carefully and to the best of their ability. The firm couldn't provide evidence to the ombudsman of the specific questions they'd answered incorrectly. They were asked to re-examine their claims decision.
The firm with the highest uphold rate for travel insurance complaints was Allianz (41%).
One published dispute involved a customer being chased for a hospital bill after a holiday in the USA. Medication for his condition had been stolen, along with a bag, so he had to attend an A&E ward to get a replacement prescription.
Allianz was initially unwilling to pay the resulting $1,700 hospital bill as the customer hadn't been ill when he sought medical attention. However, the ombudsman ruled in the customer's favour and Allianz paid the claim and compensation.
Great Lakes had the highest uphold rate of any motor insurer at 42%.
One dispute last year concerned a claim made following the theft of some tools from a van. The customer was clear the van had been secured, but the insurer wasn't satisfied there was enough visible evidence of 'forcible and violent' tampering with the lock. The ombudsman didn't feel this ruled out the possibility of the van having been broken into.
Of the four insurance areas we examined, contents insurance had the lowest overall uphold rate (27%), although with the Society of Lloyd's, the worst offender, 39% of complaints were upheld.
We looked at the proportion of complaints upheld against insurers that had received at least 30 complaints overall, and at least 10 upheld.
You can use the search bar to find your insurer and see how it fared.
Data source: Financial Ombudsman Service.
You can raise a complaint with The Financial Ombudsman Service about any firm that is regulated by the FCA. This includes insurers, banks, loans or credit card companies and financial advisers.
The ombudsman's job is to be impartial - so it's not guaranteed that it will decide in your favour. However, it's free to use and has statutory powers, meaning companies are legally obliged to comply with its decisions.
If you're dissatisfied with your insurer's service or feel you've been treated unfairly by it, start by making an official complaint directly to the insurer, ideally by letter or email. We explain what to do in
Once you've initiated a complaint, the company has up to eight weeks to provide you with its final response.
If you remain unhappy with the outcome of the complaint, then ombudsman can step in. You can get in touch through the website website (), call on 0800 023 4567 or write to Exchange Tower, Harbour Exchange, London, E14 9SR.
A backlog of more than 30,000 cases means the ombudsman does experience delays, with a third of car insurance complaints taking more than three months to resolve. However, they ombudsman is sometimes able to resolve matters informally between the customer and the company, which can be quicker.