Google has been issued a "statement of objections" by the European Union competition commissioner for indulging in anti-competitive behaviour.
While noting that the search engine's promotion of its own shopping links amounted to an abuse of its dominance in search, Margrethe Vestager gave Google 10 weeks to respond, reported the BBC.
The tech giant reacted by saying that it "strongly disagreed" with the allegations and looked forward to making its case.
Vestager also launched a probe to determine if the way Google bundled apps and services for its Android operating system was unfair.
She also added that the EU would continue to monitor Google's other activities that its rivals have complained about.
It followed a five-year probe into the company and marked the beginning of a formal legal process that could lead to huge fines.
Google accounts for more than 90 per cent of web searches in the region.