Faulty tyre pressure monitoring systems are causing thousands of MoT failures, according to new research.
TPMS, which monitors the air pressure inside the tyre to ensure safe driving, have been fitted to new cars for some years now, but they do not always warn the driver if they fail.
But the systems, if installed, need to be working in order for the car to pass an MoT, and tyre safety charity TyreSafe says nearly 20,000 tests have been failed so far - and is holding drivers responsible.
Stuart Jackson, chairman of TyreSafe, said: "Ensuring tyre pressures are correct is a cornerstone of road safety. TPMS is a potentially life-saving technology which helps the driver monitor those pressures when they need it most - out on the road.
"As with all safety systems, drivers need to check their TPMS is fully-functioning regularly, not only to pass the M0T but to help reduce the risks of a tyre-related incident whenever they drive."
In a statement TyreSafe said: "TyreSafe is urging all drivers to regularly check their TPMS is fully functional to reduce risks of tyre-related incidents on the roads. Regular checks and servicing will help ensure your TPMS system continues is operating properly.
"If the TPMS sensor does need replacing, it should never be replaced with a 'standard' valve - you're not only increasing your risks on the road but your vehicle is also likely to fail its MoT."