Red Bull slam 'underhanded' Mercedes over tyre testing Race winner Nico Rosberg of Mercedes GP celebrates with Sebastian Vettel and Mark Webber. RED Bull team chief Christian Horner has accused triumphant Monaco Grand Prix rivals Mercedes of "underhand" activity as the dust finally settled following Sunday's turbulent race won by Nico Rosberg. Horner, who joined Ferrari in lodging a protest on Sunday against Mercedes for allegedly taking part in an illegal in-season Pirelli tyres test, said he was most aggrieved at the manner in which the German team had behaved. The sport's ruling body, the International Motoring Federation (FIA) was still awaiting a report from stewards at the Monaco Grand Prix, with whom the protest was lodged. Horner said: "What is wrong is that a team, in an underhand way, consciously tested tyres that were designed for this year's championship. We view that the testing rules are very clear in the sporting regulations and when you enter the championship at the beginning of the year you sign up to those regulations. We put in a protest because we wanted clarity more than anything. We talk an awful lot about saving costs. We spent three hours on Friday (in a team principals' meeting) talking about in-season testing and trying to find a solution, and it turns out one team has already done a huge amount of it. Horner's blast at Mercedes came after seeing Rosberg produce a superb drive from pole position to resist Red Bull pair, defending drivers' world champion German Sebastian Vettel and Australian Mark Webber, who, thanks to some luck with the delayed introduction of the first Safety Car, managed to push Briton Lewis Hamilton, in the second Mercedes, back to fourth. Meanwhile, McLaren team boss Martin Whitmarsh moved to the defence of his wildly-aggressive Mexican driver Sergio Perez, who was involved in a series of dangerous attempts to force his way into passing positions. Perez was called "stupid" by Kimi Raikkonen of Lotus for causing a crash late in the race that cost the Finn fifth place. He finally came home 10th. "He hit me from behind and that's about all there is to it," said Raikkonen, who was just one of a series of drivers to be 'attacked' by the Mexican's continued use of 'GP2 tactics' in a race that also saw perennial crasher Frenchman Romain Grosjean given a penalty for his wayward and reckless racing. "If he thinks it's my fault that he came into the corner too fast then he obviously has no idea what he's talking about," said Raikkonen. It's not the first time he's hit someone in the race. He seems to expect people to be always looking at what he might do, then move over or go straight on if he comes into the corner too quick and isn't going to make it without running into someone. It was a really disappointing day... Because of one stupid move from Sergio we've lost a lot of points to Sebastian in the championship and you can't afford to lose ground like that. Not the ideal weekend, but there's nothing we can do about it... At least we got one point back at the end. Whitmarsh said: "I don't think there is too much to complain about there. That's what happens in Monaco - I am happy with his spirit and his challenge. I have to be pleased he is there, he is committed and he is racing.