McLaren, Mercedes and two other teams have been ordered to adjust their double-diffusers after the FIA closed a loophole that had been exploited.

Article 3.12.7 of the 2010 technical regulations states that: ”a single break in the surface is permitted solely to allow the minimum required access for the device referred to in Article 5.15. [supposed to refer to starter motor, although this is Article 5.16].”

However, the regulations do not state what the minimum required access is, meaning teams have exploited this loophole to create intricate shapes in the diffuser. This idea was pioneered by Brawn GP last year – had the FIA clamped down on this this time in 2009, would Sebastian Vettel be the reigning world champion?

The FIA have sent a note to all teams, containing strict dimensions for a maximum diameter for the holes and a maximum projected area, meaning that McLaren, Mercedes and two other teams will have to make modifications ahead of next weekend’s Australian Grand Prix.