The RAC said latest data shows that around 7.3million vehicles on our road fail their MOT each year, though around 2.4million of these are cars and vans with dangerous problems.
The Department for Transport (DfT) is seeking views on the frequency of MOTs - which under existing regulations are every 12 months after the first test.
Motoring groups said the proposals, the biggest shake-up of MOTs for decades, would lead to more deaths and injuries on the roads as cars and vans could be driving with defective tyres and brakes.