More than five million motorists are driving unsafe vehicles, research by breakdown service Britannia Rescue has shown.
As many as 22% of these drivers have known about the dangerous fault on their vehicle for more than six months, the company said.
A total of 31% claimed they could not afford to fix the problem, while 11% said they had not had time to get their car repaired.
The most common faults were worn tyres, defective brakes and faulty exhaust pipes.
Around 5% of the vehicles in need of repair have broken or missing wing mirrors, while about the same number have broken head or tail lights.
Britannia Rescue general manager Simon Stevens said: "It's concerning that so many motorists currently drive dangerous vehicles in need of repair.
"Some repairs may appear to be minor but they could still turn a car into a death-trap that endangers the driver, passengers and other motorists.
"It can be tempting to put off repairs but doing this could lead to you being fined and, far worse, put you and your family in danger."
