The UK’s Financial Ombudsman Service (FOS) has warned insurers they must be able to prove fraud, and should not find other ways to reject claims.

It says fraud is central to many insurance disputes, but it is clear from some cases that when insurers believe a claim is fraudulent but cannot prove it, they reject it over non-disclosure.

The service’s annual review says a consumer should have an opportunity to explain inconsistencies in their account of what happened, because there may be an innocent explanation.

FOS settled more than 518,000 disputes in 2013/14, more than double the previous year.

About 78% of cases related to payment protection insurance (PPI), a form of consumer credit cover that was mis-sold to many consumers.

Complaints about other forms of insurance were steady at 6%, and of these 52% related to claims and 31% sales and advice.

About 58% were against insurers, 16% against intermediaries, 14% against banks and 1% against Lloyd’s.

Consumers complained about travel policies not paying out when they cancelled their holidays because of relatives’ medical conditions.

FOS found some travellers had claims rejected because their insurers assumed injuries were alcohol-related.

About 53% of all travel complaints were settled in favour of consumers, compared with 39% for contents insurance, 44% in buildings insurance, 38% in motor insurance and 65% in PPI.