Lewis Hamilton's Mercedes team and tyre supplier Pirelli could face heavy sanctions after Formula One's governing body summoned them to an international tribunal for allegedly carrying out a 'secret' test in breach of the rules.
The governing International Automobile Federation (FIA) said in a statement on Wednesday that they had decided to act after conducting a full enquiry into the test that took place in Spain between May 15-17.
Mercedes used their current race car with Britain's 2008 world champion Hamilton and Germany's Nico Rosberg -- the winner from pole position in Monaco on May 26 -- sharing the driving over three days.
Rivals have accused the team of gaining a significant competitive advantage from the test and behaving in an 'underhand' fashion.
Pirelli dispute that, saying they were testing tyres for 2014 and Mercedes did not know what compounds were being used.
Article 22.1 of Formula One's 2013 sporting regulations bars in-season testing with "cars which conform substantially with the current Formula One technical regulations in addition to those from the previous or subsequent year."
However, Pirelli are allowed, under their commercial contract, a number of 1,000km tests and have previously used a 2010 Renault which they say is some four seconds a lap slower than the 2013 machinery.
Ferrari, who conducted a similar 1,000 km test at the same Barcelona circuit in April but with a 2011 car and test driver, faced no further action because they were not deemed to have contravened the regulations.
No time was set for the tribunal, which could impose stiff sanctions against Mercedes if they are found to have acted illegally.
Already under fire for their quick-wearing 2013 tyres, Pirelli have been pressing to be allowed to test with more up-to-date cars to that they can prepare for the significant challenge of a new V6 engine next year.
The Italian company has yet to agree a contract with the teams and FIA for 2014, however, which has added to their frustration.
