- Mercedes and Formula One tire supplier Pirelli called to face FIA Tribunal over tire test
- The use of a 2013 Mercedes car and drivers to test tires may breach FIA rules
- Ferrari face no further action over their private tire test for Pirelli using a 2011 car
- Mercedes face a fine or ban, including exclusion from the championship
Just 10 days after the celebrations of winning the Monaco Grand Prix, Mercedes is facing the possibility of sanctions after being called to the International Tribunal of Formula One's governing body.
The German team and the sport's tire supplier Pirelli have been summoned to explain an alleged illegal tire test to the FIA's disciplinary body.
The tribunal has the power to impose fines and bans, including exclusion from the F1 world championship.
The FIA began an investigation after rival teams Red Bull and Ferrari lodged an official protest on the morning of the Monaco race after discovering Mercedes had helped Pirelli carry out a three-day development test in Spain, which was reported by the stewards.
"The conditions of this testing may constitute a breach of the applicable FIA rules," the governing body said in a statement.
In-season testing has been banned in F1 since 2009 but Pirelli has an agreement that says it can run 1,000 kilometers of testing with any marque during the season -- as long as every team is offered that opportunity.
After gathering evidence from the Italian tire manufacturer, Mercedes and the other 10 teams, the FIA has decided that Mercedes has a case to answer -- though a date has not yet been set for the hearing before a 12-man panel.
Mercedes' rivals objected because it used race drivers Lewis Hamilton and Nico Rosberg to carry out the test in the team's 2013 car -- and it is primarily for these reasons the sport's governing body is bringing the case before its tribunal.
The rival teams have accused Mercedes of gaining a significant competitive advantage from the test and of conducting it in secret two days after the Spanish Grand Prix, where both Rosberg and Hamilton suffered tire problems despite the German having started in pole position for the second successive race.
Mercedes has struggled all season with tire degradation despite being quick in qualifying.
Rosberg took the team's first grand prix win of the season at the Monaco Grand Prix, held on a slower, street circuit that is not as harsh on tires.
Mercedes released a statement in response to the news that read: "We welcome the opportunity to explain the full facts of the Pirelli test in an open and transparent manner at the International Tribunal.
"Sporting integrity is of primary importance to Mercedes-Benz and we have the utmost confidence in the due process of the FIA."
Pirelli tried to assuage the situation by issuing a statement, prior to the FIA's summons to its International Tribunal, explaining the controversial tire test.
"The use of the car utilized by Mercedes, in particular, was the result of direct communication between FIA and the team itself," the statement read.
"Pirelli did not ask in any way that a 2013 car be used: not of Mercedes nor FIA nor the teams which, during the year, were offered the opportunity of participating in tests for the development of tires for 2014.
"Pirelli, in development testing with teams carried out in 2013, has not favored any teams and, as always, acted professionally, with transparency and in absolute good faith."
Pirelli's contract to supply tires to F1 runs out at the end of the season. The company had been close to securing a new three-year deal, but a new contract could now be in jeopardy.
In light of this, Pirelli stressed that the recent tire testing had focused on developing tires for 2014 when significant rule changes governing engines will be introduced.
Ferrari was also asked to explain a tire test carried out at the Italian team's private Fiorano test track in April.
It used a 2011 car during this test and, for this reason, the FIA concluded the team -- which used to be managed by FIA president Jean Todt -- had no case to answer.
The governing body explained that "a 2011 car is not deemed to contravene the applicable FIA rules."
The topic of tires has dominated the 2013 F1 season with many teams, including world champions Red Bull, criticizing the current specification of rubber and the number of pit stops seen during the races.
Pirelli is trialling a new "medium" compound tire at this weekend's Canadian Grand Prix in Montreal, which it then plans to introduce as the race tire for the rest of this season.
It is hoped the new tire will be safer and not split into layers, as has been seen on four occasions this season.
While Pirelli hopes to solve one problem on track, it will be left to a tribunal in Paris to rule on the tire controversy that has split the F1 community.