Mercedes 'welcome' chance to respond to tyre test claims
Mercedes say they "welcome" the chance to justify taking part in what rivals say was an illegal Pirelli tyre test.
Formula 1's governing body, the FIA, has ordered Mercedes to appear before a hearing of its international tribunal.
A Mercedes statement said they would "explain the full facts of the test in an open and transparent manner".
It added that "sporting integrity is of primary importance to Mercedes" and they had "the utmost confidence in the due process of the FIA".
The FIA said in a statement on Wednesday that it had decided after receiving a report from Mercedes into the test that "the conditions of this testing may constitute a break of the applicable FIA rules".
Mercedes did 1,000km of running over three days at Barcelona's Circuit de Cataluya on 15-17 May, using a 2013 car and race drivers Lewis Hamilton and Nico Rosberg.
Article 22 of the F1 sporting regulations explicitly forbids "using cars which conform substantially with the current Formula 1 technical regulations in addition to those from the previous or subsequent year".
Mercedes say they discussed the test with the FIA beforehand and believed they had been given permission to use a current car.
Red Bull's reigning world champion Sebastian Vettel believes Mercedes should be penalised.
"It takes the official way now and we will see what happens," he said. "It is very unlikely that all of a sudden all the other teams can have a go, but at the same time there must be some kind of penalty because I think it's just not allowed. But what the penalty is, I don't know. It's for the experts to find a solution.
"It would be a big advantage compared to everyone else if you are the only one to do it. If everyone does it, it is the same for everyone but clearly that hasn't been the case for all the teams."
The FIA has decided Ferrari have no case to answer after using a 2011 car in a similar manner at a test the previous month.
This is the first time the international tribunal - an independent panel chaired by a leading lawyer - has been used in this way.
It is part of attempts to increase the transparency of the FIA process by president Jean Todt, who can be present at the hearing only as an observer.
Todt is the former team boss of Ferrari, where he worked closely with Mercedes' current team principal Ross Brawn.
The tribunal has powers to impose a wide range of penalties, ranging from exclusion from the world championship right down to no penalty at all.
Previous punishments imposed by the FIA include:
- McLaren being fined $100m and stripped of all their constructors' points for 'spying' on Ferrari in 2007
- BAR-Honda being banned for two races in 2005 because of an illegal fuel tank which the team could not prove did not allow them to run the car underweight.
The Mercedes tyre test came to light at the Monaco Grand Prix. On race morning in Monaco, Red Bull and Ferrari launched an official protest, accusing Mercedes of breaking article 22.4 of the sporting regulations, which defines what testing can be done in a season.
Pirelli has defended the test, saying it was neither secret nor inappropriate.
It has an agreement with the FIA that allows it to do tests up to a maximum of 1,000km if it feels it needs them to develop its tyres.
Pirelli is trying to change the rear tyres used in F1 this year to prevent a series of embarrassing failures. Teams will be trying a development tyre at this weekend's Canadian Grand Prix.
Pirelli, which does not yet have a contract to continue as F1's tyre supplier in 2014, is also concerned that the new turbo engines being introduced next season will impose far heavier demands on the tyres than this year's cars.
It says that the Mercedes test was "90%" to do with 2014, with only the remainder devoted to running a development 2013 rear tyre.
Rivals are outraged that Mercedes - the team that has been struggling most with excessive rear tyre usage in races this season - should have the chance to try the tyres before them.
Red Bull team principal Christian Horner said: "What is wrong is that a team, in an underhand way, consciously tested tyres that were designed for this year's championship."
Pirelli says the test was "blind", that Mercedes did not know which tyres were being used at any time and that the team were not allowed to change the set-up of the car".
The FIA said after Monaco that "at the beginning of May, it was asked by Pirelli if it was possible for it to carry out some tyre development testing with a team, using a current car.
"Within the contract Pirelli has with the FIA as single supplier, there is provision for them to carry out up to 1000km of testing with any team - provided every team is offered the opportunity to do so.
"Pirelli and Mercedes-AMG were advised by the FIA that such a development test could be possible if carried out by Pirelli, as opposed to the team that would provide the car and driver, and that such tests would be conditional upon every team being given the same opportunity to test in order to ensure full sporting equity."
Rivals say they have not been offered that opportunity. Pirelli says it sent an email to all the teams last year asking about the subject and received almost no replies.
Pirelli's conduct is also under investigation as part of this process and it could face penalties under the FIA code, although the sporting regulations do not apply to it.