Microsoft on Wednesday lodged a formal complaint with the European Union's competition regulator against Motorola Mobility and its soon-to-be owner Google, saying Motorola's aggressive enforcement of patent rights against rivals breaks competition rules, according to AP. The complaint follows a similar step by Apple against Motorola last week. Motorola is in the process of being taken over by Google for $12.5 billion, the biggest acquisition in the Californian company's history. Microsoft fears that Google will continue Motorola's tight hold on key patents. Apple Inc. and Microsoft Corp. have been hit by legal cases in Europe and the United States, with Motorola claiming that the companies' products are using key patents it owns without permission. Apple and Microsoft, meanwhile, argue that Motorola is overcharging for the use of these patents, which cover technologies necessary to connect wirelessly to the Internet or stream video online.