Melbourne - BMW-Sauber Thursday filed a protest against rival teams Brawn GP, Williams and Toyota over their cars three days ahead of the Australian Grand Prix.

BMW motorsport director Mario Theissen said the team was protesting over the use of the three teams' diffusers.

Protests from Ferrari, Renault and Red Bull were expected to follow.

The dispute centres around the rear diffusers, a part of the bodywork between the rear wheels and under the rear wing which disperse air from under the car.

It is claimed the designs of the Brawn GP, Williams and Toyota cars will give them an unfair speed advantage going into the start of the season.

New regulations limit the size of the diffusers but the three teams have found a potential loophole in the rules by designing the rear bodywork to effectively act as part of the diffuser, increasing its size.