The European Commission (EC) could hit Google with a significant fine for its attempts to enforce an injunction to stop Apple selling its iPhones in Germany.
The Commission made the antitrust finding against Motorola Mobility, which Google acquired last year for $12.5bn (£8bn).
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In its statement of objections, the EC said Motorola Mobility's use of mobile phone standard-essential patents (SEPs) "amounts to an abuse of a dominant position prohibited by EU antitrust rules".
The SEP in question is of a General Packet Radio Service (GPRS) standard, part of the Global System for Mobile (GSM) communications.
The Commission went on to state that Apple was willing to enter into a licence on fair, reasonable and non-discriminatory terms, and as a result, Google, as the dominant SEP holder, should not have had to resort to enforcing an injunction against the Cupertino-based firm.
"The protection of intellectual property is a cornerstone of innovation and growth, but so is competition," said the EC's vice president, Joaquín Almunia, who is in charge of competition policy.
"I think that companies should spend their time innovating and competing on the merits of the products they offer - not misusing their intellectual property rights to hold up competitors to the detriment of innovation and consumer choice," he added.
Google-owned Motorola Mobility has not fared well in several intellectual property cases against rivals Microsoft and Apple.
Last month, Apple ensured it wouldn't face an import ban on its iPhones, after it persuaded a US trade agency that it did not infringe a sensory patent, owned by Motorola Mobility - this was the sixth and final patent still to be in dispute between the companies in the US, Motorola had lost the other five cases.
In the same week, US District Judge James Robart ruled that Microsoft owed Google $1.8m (£1.16m) over wireless and video patents, far less than the $4bn (£2.6bn) that Google had been claiming.
The Commission's current case will do further damage to a portfolio of 17,000 Motorola patents, which Google had valued at about $5bn (£3.2bn).
Motorola has two months to respond to the charges and the Commission will only make a final decision after the company responds.
If Motorola responds, and the Commission concludes that there is sufficient evidence of an infringement, it can impose a fine of up to 10 per cent of the company's annual worldwide turnover.
