The first information on which cars are most likely to cause whiplash injuries in drivers and passengers is due to reach motor insurers by April.

The rolling programme of research by Thatcham, the Motor Insurance Repair Research Centre, has already produced data on 12 makes of car.

Thatcham is currently studying how to present the data so that insurers can easily incorporate it into their premium pricing structures.

According to Thatcham's research director Ken Roberts, the results of tests on bumpers and head-rests tallied with the cars' general safety records in most cases, but one or two vehicles' results "raised eyebrows".

He was also disappointed to find that manufacturers did not appear to be improving seat and head-rest design when they up-dated models. "We're finding that fourth generation models are not necessarily better than the second or third versions," he said.