Melbourne  - A row was looming ahead of the start of the Formula One season with leading teams questioning the legality of the bodywork of three of their rivals including newcomers Brawn GP.

A rift appeared to open Wednesday ahead of Sunday's Australian Grand Prix in Melbourne, with Red Bull saying it would lodge a protest if the Brawn GP, Williams and Toyota cars were allowed to race as they now stand.

Governing body FIA is set to check whether the cars conform to the regulations on Thursday.

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.

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.

Red Bull team adviser Helmut Marko said a protest will be lodged if those teams are passed to compete following Thursday's examination by FIA.

"We'll make a protest on Thursday if the component isn't modified to conform to the regulations, because that diffuser guarantees a five-tenths (of a second) advantage per lap," Marko told Sky Sports.

"Seven teams are certain it's illegal."

Ferrari team principal Stefano Domenicali said he wanted the issue to be solved quickly to prevent the dispute overshadowing Sunday's opening race.

"We are convinced that certain interpretations that have been applied do not correspond to the nature of the rules," he said.

"If that extractor is illegal then it must not be used, while if it is legal it's up to the other teams, including us, to try to adapt as soon as possible, because performance is found in that area of the car.

"There needs to be a great sense of responsibility on everyone's part. I hope this issue can be resolved beforehand."

Brawn GP, which has succeeded Honda, has now emerged as the team to beat in Sunday's opener following impressive test times.

Australian bookmakers have made Brawn GP's British driver Jenson Button, who has won just one race in 153 Grands Prix, the favourite for Sunday's race.

Williams team boss Sir Frank Williams said: "They will disappear on the basis of what we have seen in testing. I just hope we can be up there, too." (dpa)