Studies from the industry body have indicated that out of 30 manufacturers surveyed, 83% were rated as above average, with Lexus and BMW achieving the highest results.
Alan Pulham, franchise dealer director at the RMI, said: 'Manufacturers have listened on the parts issue, which is encouraging, but one wonders if this is only because of the public outcry that the shortages caused.'
Rover has managed to climb from the bottom of the table after dealing with problems it encountered in 2002. It addressed the issue last year when its sister company Xpart agreed to quote a completion time when parts were ordered.
If Rover failed to meet the deadline due to the late arrival of parts, a special Parts Pledge programme covered the cost of a courtesy car until three days after the parts were delivered.
Last year, the Association of Car Fleet Operators (ACFO) launched an initiative aiming to reduce the number of occasions when cars were off the road due to a lack of spare parts following an accident or mechanical failure. The move has won support from 21 manufacturers who have agreed to take steps to end the problem.