Only eight out of 36 MOT tests in a recent Which? undercover investigation were carried out correctly, and the magazine says an increasing number of garages were passing faulty cars compared to a similar exercise carried out five years ago.

Which? is lobbying for Vosa to carry out an urgent investigation into why cars which should obviously have failed the MOT were passed.

For its latest investigation, Which? bought six used cars between three and 10 years old, and then introduced a variety of faults to them, some of these serious enough to stop the car passing an MOT. Each car was taken to six different garages, 36 garages being visited in total.