Fleet managers need to be fully aware of the cost of repair before ordering new cars after the latest series of tests revealed that even a low-speed crash can result in thousands of pounds worth of repairs.

A Subaru Impreza tested by Thatcham, the motor insurance repair research centre, during its latest bumper tests found that if the car was in a 6mph crash it will cost £4,151 to repair.

Following the tests, which are designed to replicate the most common type of crash, the damage to the Subaru was so extensive the car was not drivable.

“The Impreza was the worst performer in Thatcham’s 2008 bumper tests,” said Thatcham.

“The car achieved its poor rating because of the severity of damage and excessive repair costs.”

While Subaru points out the tests are not part of Thatcham’s insurance group rating assessment, the test centre warned: “If the insurer identifies that the repair costs on a particular vehicle are consistently higher than other vehicles they will look to mitigate their risk and adjust premiums accordingly.”

Mark Norman at CAP said while fleets may already be taking action, they need to be aware of any knock-on effects of the tests: “In terms of whole life costs it is unlikely to have any visible effect on individual models as many fleets already tend to exclude higher insurance group vehicles from choice lists already,” he said.

“Where costs are likely to be pushed up by this is via any further rises in insurance premiums due to higher repair costs.”

Most of the 12 vehicles tested achieved only ‘poor’ or ‘marginal’ ratings, with only one achieving an ‘acceptable’ rating in the rear bumper test - the Ford Focus, which would cost £789 to repair.

The Focus was also the best performer at the front with the lowest repair cost of £1,556.

Nine of the 12 cars tested needed their headlights replacing.

The Impreza’s headlights were the most expensive to replace at £382 each.

Subaru said: “While the quoted cost of repair within the report is of concern, we have no details of the items involved and cannot therefore comment further.

"We are constantly monitoring parts prices, particularly in relation to minimising cost for low impact accident repairs.”

Thatcham warned that some bumpers were below standard and did not provide the protection expected.

“Many bumper systems do not protect the rest of the car from damage because they are too weak, poorly aligned, too small, or in some cases, not there at all,” it said.

The bumper tests are based on a new international standard bumper test from RCAR (the Research Council for Automobile Repairs).