Red Bull's Helmut Marko has hit back at Michael Schumacher after the seven time world champion accused the team of breaching the rules about staff numbers.Earlier in May 2011, the Mercedes driver referred to a clause in the Resource Restriction Agreement when he said "certain teams don't respect that"."If you take the number of people we have compared with Red Bull, that is very different," said Schumacher.Indeed, Mercedes employs 400 people at Brackley, plus 20 for administration and marketing in Stuttgart.Red Bull, meanwhile, has 550 staff at Milton Keynes.Marko told Auto Bild: "The agreement never came into force. We were reluctant because it (the staff limits) were purely for the chassis development."He said if F1 teams want to limit staff numbers, then the limit should also apply to the development of engines.For instance, Mercedes employs another 400 people for the development of its F1 engines, while Red Bull's supplier - Renault - has just 170 staff at Viry-Chattilon."Mr Schumacher should be asking how many people work on his Mercedes engine in Brixworth," said Marko."Why should we make concessions in the development of the chassis when Mercedes has every freedom for the engine?"