Road safety charity the Institute of Advanced Motorists (IAM) is warning that some popular aftermarket vehicle mods are putting lives at risk.

The charity has highlighted three common aftermarket modifications that both render vehicles illegal and offer a threat to road users, although people are rarely prosecuted for carrying out the work. Removing the DPF, fitting Xenon headlights and reprogramming / chipping vehicle ECUs are highlighted as the most dangerous.

IAM head of technical policy Tim Shallcross comments: "DPF removal has always been illegal but since 1 January 2014 has also been reason to fail an MOT. Some garages are blatantly still doing it. In short - they are selling a service that's killing people. Removing a DPF isn't a task that can be done accidentally, as it involves reprogramming the engine management computer. Before 1 January it wouldn't count as an MOT fail but unscrupulous traders still offer to cut the case open from the top of the unit, remove the filter and welt it shut again - in an attempt to pull the wool over the eyes of the tester to achieve an MOT pass. This is disgraceful, but people are rarely prosecuted for this openly advertised service."

The popular trend for xenon headlamp conversions is also a major hazard - not having a self-levelling or washing function means they can dazzle oncoming traffic, potentially causing an accident. Finally the reprogramming of ECUs or 'chipping' is another popular modification that is fraught with hazards for a number of reasons.