Any vehicle dating from before 1977 is to be classified as a classic, under new government plans.
The proposed changes, which will come into effect within the next two years, aim to make it easier to keep older cars on the road.
Previously, all vehicles built after 1960 were subject to an annual MOT. However, with stricter emissions and safety regulations than ever before, many cars such as the Morris Marina and Austin Allegro stand little chance of passing. With their new 'classic' status, more than 331,000 such models will be exempt from the testing.
The government attributed this new allowance to the fact that many cars built in the 1960s and 1970s are now considered collectors' items. As such, they are often maintained to a higher standard by enthusiasts than newer models, despite being driven far less often.
However, critics have attacked these reforms, claiming that the move puts the public at risk.
Quentin Willson, journalist and spokesman for FairFuelUK, said: "You're talking here about cars like the Escort Mk1 and the Cortina. They were hardly at the zenith of rustproofing or technical efficiency and need constant maintenance.
An EU proposal had originally suggested the threshold should exempt vehicles older than 30 years from the MOT process. However, a consultation document published by the DfT yesterday rejected this but recommended the 40-year cut-off point.
This will bring MOT testing in line with the vehicle tax system, as cars more than 40 years old are already exempt from vehicle excise duty.