The opening round of the 2009 Formula One world championship took the anticipated negative turn after protests against three of the pre-season pacesetters were officially protested for running diffusers believed to contravene the new regulations.

Toyota, Toyota-powered Williams and the surprise package Brawn GP all had their machines called into question on the eve of practice at the Australian Grand Prix, as the simmering row over interpretations of the rules covering diffuser design erupted once again. Toyota and Williams had their parts queried soon after their respective cars were launched, while Brawn's pre-season pace has also been put down, in part, to the team's reading of the rules.

It is understood that the protests have been lodged by the BMW Sauber team, but will likely have received tacit support of others in the Melbourne pit-lane as Renault and Red Bull Racing have both indicated that they would have taken the same action if necessary.

"We will lodge a protest," BMW team principal Mario Theissen told reporters earlier in the day, "We are preparing our protest and then we will see what happens."

The new-for-2009 aerodynamic regulations state that the rear diffuser must not exceed 175mm in height, and the bone of contention is that, initially, Toyota and Williams and, on its belated launch, Brawn GP appear to have interpreted the regulation in such as way as to use 'sculpting' of the rear crash structure to enable their diffusers to rise above that measurement.

"Toyota's diffuser makes a very interesting interpretation of the revised 2009 rules (and one that has already prompted speculation regarding its legality)," the official F1 website explained during the pre-season build-up, "By exploiting regulations that allow extra bodywork within a 150mm zone in the centre of the car, the team appear to have cleverly shaped the TF109's rear crash structure so that it effectively lengthens and heightens the diffuser's central section, which also features a very low splitter at its base.

"Like engine supplier Toyota, Williams' interpretation of the revised diffuser regulations is highly innovative. Much of the diffuser's central section is actually lower than the outer sections. However, clever shaping of the rear crash structure immediately below the rear light effectively creates a second central section. In combination, the result is a central section that exceeds the 175mm height allowance that applies to the diffuser alone."

While both Williams and Toyota are understood to believe their designs have been given the all-clear, no official protest could be lodged before the teams arrived in Melbourne and, even though all cars passed successfully through the first scrutineering session of the weekend, renewed action was always expected. Brawn's late arrival on the scene prevented detailed analysis of its design, but the team has been drawn into the mire since arriving in Australia for the opening round, with reports suggesting that its BGP001 links the floor of the car with the diffuser in such a way as to 'significantly increase rear downforce'.

Intriguingly, the BBC has reported that Toyota has an alternative diffuser on hand and could, if necessary, race with that if the protest is deemed valid, but, should the protested cars be deemed legal, there would be renewed efforts elsewhere to develop similar parts for future races. Except maybe at Red Bull, whose unique pull-rod rear suspension would require a major redesign to incorporate a Brawn or Williams-style diffuser.

McLaren, meanwhile, has distanced itself from the protest - maybe due to Brawn sharing a common Mercedes engine - but insists that the sport needs the issue to be cleared up as soon as possible.

"Sadly, a lot of the column inches this weekend are going to be about controversy - and it can easily become acrimonious," new team principal Martin Whitmarsh admitted, "That's the way of Formula One, to sometimes stumble across into a very acrimonious environment. In defence of everyone, I don't think anyone has set out deliberately to cheat here, and it's a shame that this sporting occasion is going to have that controversy thrust upon it over the course of the weekend."

Whitmarsh admitted that he was keen to have the FIA reach a consensus on the diffuser issue, as it could provide the McLaren team with a means of closing the performance deficit it appeared to suffer in pre-season testing.

"We have an underdeveloped car, we do not have sufficient aerodynamic downforce and we'd like to focus on rectifying that situation as quick as we can," he conceded, "In order to do so, it would be very handy if I could tell our aerodynamics team that these are the rules that prevail. I can't actually do that today, which means that you've got a foot on the bank and a foot on the boat. Either the majority of the teams are going to have to change the design of their car or the minority are going to have to change theirs."

FIA president Max Mosley, while vowing not to get personally involved in what is a matter for the governing body's technical experts, has admitted that he can see the row rumbling on through the first few rounds of the season, with results held in limbo until a decision can be reached.