The governing body of motorsport argued Thursday that Mercedes broke the rules and got an unfair advantage over other Formula One teams by taking part in private in-season tyre testing with Pirelli.
Mercedes and Pirelli were answering the charges at a disciplinary tribunal hearing in Paris. It was convened by the International Automobile Federation (FIA).
Laying out the case for FIA, lawyer Mark Howard said Pirelli tried out a variety of tyres over 1,000 kilometers (620 miles) of track tests in May in Barcelona. Mercedes' 2013 cars, driven by current drivers Nico Rosberg and Lewis Hamilton, were used and this offered an advantage to the German team, Howard argued.
"They have been enabled to do something which the other teams have not done," he said. "By testing the Mercedes car for three days, the 2013 car, with the current drivers and the current engineers, Mercedes may be said to have obtained an unfair advantage."
Pirelli organized the tests and paid for the Barcelona circuit where they were held, Howard said. But he argued that the testing could still have provided Mercedes with potentially valuable information about its cars and their reliability.
"Clearly there was data that was available to Mercedes," he told the panel of judges. "It is difficult to say that Mercedes gained no benefits from the test."
Howard noted that Mercedes, in particular, has struggled with the wear and failures of Pirelli tyres this season. He suggested other teams might have objected in advance about the test had they known about it.
Howard spoke for 1 hour, 40 minutes. Mercedes, represented by team principal Ross Brawn, lawyers and others, will present its defense later along with Pirelli.
Howard said none of the other F1 teams were invited to the testing and none were aware it was taking place.
"There is in fact very little factual dispute in this case," he said. "If Pirelli and Mercedes had been transparent and open about what was going on" then all the other teams would have been able to say whether or not they objected to the testing beforehand.
F1 rules ban the use of current-season cars for track tests.
Red Bull and Ferrari later protested about the testing.
Pirelli has denied breaching any rules and said testing offered no advantages to Mercedes.
Pirelli motorsport director Paul Hembery has previously said the tyre compounds tested are not going to be used in the 2013 season.
"The focus was on 2014," Hembery said. "These tests were actually performed blind. Mercedes had no idea and has still no idea what was being tested. There was no benefit to them. The benefit was for Pirelli and F1 in general."
However, Howard said at the hearing that Pirelli told Mercedes the main reason for doing the tests was to understand and solve the acute problems with tyre wear and failure that have afflicted Mercedes this season.
The FIA also looked into another Pirelli tyre test involving Ferrari in Barcelona in April. But FIA President Jean Todt, who worked for Ferrari from 1993 to 2009, closed that case. The FIA said the Italian team used its 2011 car for the test, breaching no rules.
Howard called the Ferrari test "a complete red herring."
The FIA said the tribunal ruling "will be published as soon as possible after the hearing."