At least four teams will have to modify their diffusers ahead of next weekend's Australian Grand Prix after an FIA clampdown on a regulations loophole. The loophole in question allowed teams to create a large hole in the centre of their diffuser to improve its performance by designing an equally large engine starter motor which is connected to the car through the diffuser to start the car.

The precise wording of the regulations allows a minimum size hole in the diffuser for the engine starter motor but does not specify any maximum dimensions, meaning teams were able to aerodynamically exploit the hole by designing a novel engine starter motor.

However, Autosport is now reporting that the FIA has written to the teams specifying the maximum dimensions allowed for the engine starter motor and hence for the corresponding hole in the diffuser. As a result, frontrunners McLaren and Mercedes will have to modify their diffusers ahead of next weekend's race, while Renault and Force India are also understood to be affected too. Ferrari and Red Bull are not however.

The results of last weekend's Bahrain Grand Prix stand nevertheless, despite McLaren's Lewis Hamilton racing to third with the controversial diffuser.