Mercedes' F1 tyre test was not a secret, says Pirelli
Pirelli's sporting director says the controversial tyre test with Mercedes was neither secret nor inappropriate.
Red Bull and Ferrari lodged an official protest after the tyre supplier used Mercedes for a three-day session.
Pirelli have denied rival teams' claims it could give Mercedes an advantage.
"Some people say it's secret," said motorsport director Paul Hembery, "but we booked the circuit in our name two days after an F1 race where people turn up and take photos.
"We would be very bad spies."
Pirelli insist the test, after the Spanish Grand Prix on 12 May, was "blind" to Mercedes, in that the team were not informed any of the tyre specifications Pirelli wanted to run. While some of the testing was on an issue with the 2013 tyres, Pirelli say the majority of time was spent on developing specifications for 2014.
Red Bull and Ferrari accused Mercedes of breaking article 22.4 of the sporting regulations, which forbids in-season testing other than for a single three-day young driver test or for very limited straight-line aerodynamic tests.
Pirelli say they are allowed to ask teams to do up to 1,000km of testing, which was as much as Mercedes did over three days at the Circuit de Catalunya.
"We are developing a tyre in the 2014 F1 championship," added Hembrey of the test.
"We used tyres [during the test] that were not being used in the 2013 championship - our focus was for 2014.
"We had contacted a number of teams and Mercedes offered their availability. We determined the test. This was a blind test for Mercedes - they had no idea what was being tested."
He added that Pirelli had been working on a way to prevent this year's tyres from delaminating - when a tyre fails as a result of a puncture - so spectacularly, as some have done this year.
"We have been working on a delamination issue for the 2013 tyres - which has seen a small number of incidents," he said.
A new specification of this year's tyres will be given to every team for the next F1 race in Canada, to be run during the first two practice sessions, to ensure every team is happy that the nature of the revised tyre is consistent with what they have used so far during 2013.
Should all teams agree to use the new specification, it would be introduced for the British Grand Prix.
A statement released by the FIA at Monaco said the governing body "may bring the matter before the International Tribunal".
It added that under the terms of its contract with the tyre manufacturer it had allowed Pirelli to carry out some tyre development testing with a team, using a current car, "provided every team is offered the opportunity to do so".
It adds: "Following this communication, the FIA received no further information about a possible test from Pirelli or from Mercedes-AMG. Furthermore, the FIA received no confirmation that all teams had been given an opportunity to take part in this test."
The International Tribunal, effectively for these purposes the FIA's court, can impose any number of penalties, ranging from exclusion from the world championship to a fine.