The Financial Ombudsman (FOS) has warned drivers that car modifications can leave them with large unexpected bills.
It has said it is hearing from an increasing number of people who have been left to pay huge sums because they have unknowingly invalidated their car insurance.
Car modifications can range from body kits and custom paintwork to performance enhancements such as upgraded exhaust systems or engine tuning.
It said that whether motorists are changing alloy wheels for extra style or remapping the electronic control unit (ECU) for engine performance, not declaring modifications can have serious consequences.
It is seeing cases where a failure to declare modifications leads to insurance being invalidated or claims being rejected in the event of an accident.
The ombudsman has also suggested that when purchasing a vehicle, buyers should ask more questions and examine the paperwork to understand if any previous modifications have been made.
Rachel Lam, ombudsman director of insurance at the FOS, said: ‘For many people a car is their pride and joy, and it’s understandable that they may want to modify or personalise their vehicle.
‘But these changes can have huge repercussions – increasing premiums, invalidating insurance or leaving unsuspecting car owners thousands of pounds worse off.
‘It is crucial owners inform insurers of any modifications, even if they were made before the car was purchased.
‘If people don’t feel they have been treated fairly by their insurer, they can come to our service, and we will investigate their complaint. Getting a fair answer is free and easy.’
The FOS detailed one case where a consumer said they didn’t realise the larger alloy wheels his car had were not standard.
It felt that the average consumer would not be able to tell the difference and that they had taken reasonable care when applying for their insurance.
The service also said it found cases where consumers had declared the modifications but when they claimed they found that the value of these was not covered.