Serious issues could result in a fine of up to £2,500 if not addressed, it says.
Protyre, which has 150 nationwide garages, believes that its findings could apply to 9,550,000 vehicles on UK roads.
Protyre’s national retail operations manager, David Sholicar, said: “Most drivers breathe a sigh of relief when their car passes its MOT, but the advisories are a warning that your vehicle could still become unroadworthy in a matter of weeks if you ignore them.
“For example, a tyre advisory could be because the tread is nearing the 1.6mm minimum depth, or the tyres may have cracking due to the tyres age, or a brake advisory could be because the brakes are nearing the wear limit, or showing signs of deterioration– potentially posing a safety risk to you and your passengers.
“Despite poor tyre maintenance and faulty brakes being the top two most common reasons for vehicle accidents in Britain, they are the most common advisory for cars that pass their MOTs.
“Some research even suggests that as much as half of British drivers even ignore warnings of a faulty car part until payday.”
The Department for Transport (DfT) estimates there are 38.2 million registered vehicles on the road, however, there could be more vehicles operating with faults than first thought.
However, 1 in 6 drivers who pass their MOT leave the forecourt with the recommendation to have them fixed.
Driving a vehicle with faulty tyres, brakes or parts could see a driver given a fine and 3 penalty points.