Car owners who choose to have their Diesel Particulate Filter removed could be invalidating their insurance and breaking the law, a major motoring magazine has found.

Auto Express investigated 10 DPF removal companies, with most not informing them that their modification will affect the performance of their car, and thus affect their insurance policy.

The Association of British Insurers told the magazine that motorists should “tell their insurer about any modification”, with one saying it would decline to cover cars with their DPF removed due to the ECU needing reprogramming after removal.

Most garages wrongly stated that it wasn’t essential to tell insurance companies as the modification is difficult to detect, and wouldn’t contravene the Road Vehicles (Construction and Use) Regulation 61A (using a modified car on the road which no longer meets the emissions standards applied to it when new).

With the MOT not fully enforcing these regulations, vehicles passing the basic diesel smoke opacity inspection will still pass.

According to the magazine, the UK Government is also not enforcing European Commission Directive 2010/47/EU which states that if the exhaust emission control equipment is missing, then the car isn’t roadworthy.

Although there is no legal precedent set, it would be wise for owners of cars to think about the impact of modifications to their vehicle’s emissions system.