Masterlease surveyed 1,700 UK drivers and found that 80% admit their mirrors are not aligned correctly.
The study comes soon after the Department for Transport published figures as part of its road casualties report revealing that 15,000 UK motorists were involved in an accident as a result of their vision being affected.
Recent reports have blamed poor car design for restricted views, but Masterlease says most problems with blind spots would be eradicated if mirrors were correctly adjusted.
The company’s risk management expert Gavin Jones said the accidents could be easily prevented and urged fleet managers to ensure drivers have their mirrors lined up correctly.
He said: ‘The mirrors are there for a very good reason but, according to our study, drivers are not making the best use of them and this is leading to unnecessary accidents.
‘When a driver is concentrating on the road ahead, it is all too easy to lose track of cars overtaking or changing lanes to the rear, especially if mirrors are not in the right place.’
Jones said the problem was particularly serious if different people shared the same vehicle. He advised the best way to test mirrors are lined up correctly is to get someone to walk around the car. They should be visible in at least one of the mirrors at all times.
Step by step guide to adjusting your side mirrors
1. Move your driver's side view mirror outward
Roll up the window and press your head against the glass. Adjust the mirror so that you can just see the edge of the car. Remember, you should be looking back down the lane beside your driver's side, not at the side of your car.
2. Move your passenger's side view mirror outward
Place your head in the centre of the car (directly behind the inside mirror mount) and adjust the outside mirror so that you can just see the edge of the car.
3. Check to see what your mirrors show
When you're in your normal driving position, you won't be able to see the sides of the car but will be able to see other vehicles in the adjacent lanes.
4. Ask a friend to walk around the back of your car
As your friend circles your car, make sure that he can be seen from every angle. As he moves from your rear view mirror to go to your passenger mirror, you should be able to see him at all times. Likewise, there should be no interruptions in continuity as your friend travels from a rear view to a driver's side view in your mirrors. You haven't got it right yet until all blind spots behind you are removed!