Ferrari on Friday fiercely rejected claims by archrival McLaren that it won the season-opening Australian Grand Prix with an illegal car.

The accusation, the latest chapter in an off-track tussle sparked by the Formula 1 'spy' scandal, was "serious and false", Ferrari said in a statement.

"Contrary to what McLaren said, Ferrari has never benefited from any advantage obtained illegally. The two cars used in the Australian Grand Prix were judged to be in conformity with technical rules by stewards before, during and after the event," Ferrari said. "If there had been any illegality, they would have been disqualified," it added.

The allegation of illegality was made by McLaren CEO Ron Dennis in a letter to Luigi Macaluso, head of the Italian motorsport authority.

In the August 1 letter, Dennis drew attention to a floor device used on the Ferrari cars in Melbourne and later judged illegal by Formula 1 governing body FIA.

"It seems clear that Ferrari had an illegal competitive advantage," Dennis wrote.

After the Australian Grand Prix, won by Ferrari newcomer Kimi Raikkonen, McLaren drew the FIA's attention to the floor attachment. FIA confirmed it was illegal and Ferrari did not use it again.

Ferrari said this was a standard case of FIA clarifying an ambiguous point in technical rules and teams then making necessary adjustments.

"You could cite countless examples from the recent past involving other teams," it said.

Dennis's remarks on the Ferrari floor device were just part of a hard-hitting denunciation of the Italian team in his letter to Macaluso.

He also accused Ferrari of spreading "misleading" information about the details of the affair and of making unjustified accusations at McLaren's expense. "At the coming hearing of the FIA's international court of appeal Ferrari will fully lay out its position regarding the entire business," Ferrari said.

The dispute between the two racing teams risked overshadowing this weekend's Hungarian Grand Prix, where they were to face off on the Hungaroring.