Badly-designed car bumpers cost drivers £250m a year in unnecessary bills, an industry research centre claims.
Better car bumpers would lower repair costs, Thatcham says
The Thatcham centre said a 10mph shunt could lead to a £4,000 bill because of different bumper heights and widths.
Crash lab manager Matthew Avery said motor manufacturers were "cashing in as a direct result of design failures".
But the Society of Motor Manufacturers and Traders said bumpers were designed to strict safety standards and should not be changed just to save money.
They were intended to protect pedestrians and absorb the impact in the event of a crash, a spokeswoman said.
The Thatcham report said 4x4 vehicles made the problem worse, as they often overrode the backs of small cars.
Mr Avery said: "Many of these low-speed shunts are causing huge amounts of damage - totally out of proportion with the scale of the accident," he added.
Bills of thousands of pounds would be reduced to just a few hundred pounds if bumpers were properly positioned and strengthened, he said.
"How often do you see a woman and her children stranded by the roadside having had a minor accident when with the right kind of bumper protection she could have driven to safety?"
Current European law was "woefully inadequate" with bumpers only having to withstand a simple pendulum test, he added.
Thatcham is leading an international initiative to create an industry-wide protocol to ensure all bumpers provide proper protection.