There are concerns that if Mercedes is cleared of flouting Formula One rules after carrying out tyre testing with Pirelli last week it would open the door for others to carry out tests and lead to the renewal of a 'spending war'.
Mercedes could be stripped of points, fined or even excluded if the Monaco winners are found to have broken the rules.
The Red Bull and Ferrari teams have accused Rosberg's Mercedes team of acting illegally but Mercedes are adamant that they have done nothing wrong.
In-season testing has been banned for years, a move agreed by all teams to keep costs down, although Pirelli can conduct their own limited tyre tests with an older car.
Yet Mercedes and Pirelli managed to hold a three day, 1,000 km test at Barcelona's Circuit de Catalunya, in the week after this month's Spanish Grand Prix, with a 2013 car.
Should they be cleared, that would open another can of worms since it would open the door for others to carry out tests and might lead to the renewal of a 'spending war'.