Google has long stressed that Android, its popular mobile software, is open for anyone to use, including its rivals. But the company’s claims are now under threat after Europe’s antitrust authorities Wednesday charged the company with unfairly using Android to promote its own services — like mobile search — over those of its rivals. In doing so, regulators brought particular scrutiny to Google’s relationships with some of the world’s biggest cellphone makers, which have helped expand the reach of Android. Margrethe Vestager, the European Union’s antitrust chief, said Google had required some of the cellphone manufacturers to pre-install the company’s services, including its Google Play smartphone application store, and had given them unfair financial incentives to favor Google’s services on their mobile devices. Those practices undermined competition and consumer choice, she said. “Google has abused its dominant position,” Vestager said Wednesday. The company’s “behavior has harmed consumers by restricting innovation in the wider mobile space.” The company denies it has broken European competition rules, and the charges may not lead to financial or other penalties against Google, which now has three months to respond to the accusations. “We take these concerns seriously,” Kent Walker, Google’s general counsel, said in a blog post. “But we also believe that our business model keeps manufacturers’ costs low and their flexibility high, while giving consumers unprecedented control of their mobile devices.” By taking aim at Android — the mobile software that holds more than 80% of the worldwide market share for smartphone operating systems — Europe has opened the latest chapter in its continuing battle with US technology companies.