EU competition commissioner Margrethe Vestager told Britain's Telegraph newspaper that the threat to split up the search behemoth must be kept as an option.
Vestager said the officials in her department harboured "grave suspicions" about Google which dominates the EU search market with 91.5%.
Google was fined €2.42 billion (US$2.7 billion) by the European Union in June last year for allegedly abusing its search engine dominance to give illegal advantage to its own comparison shopping service. The company has appealed the decision.
"But Google's strategy for its comparison shopping service wasn't just about attracting customers by making its product better than those of its rivals."
She added: "Instead, Google abused its market dominance as a search engine by promoting its own comparison shopping service in its search results, and demoting those of competitors.
"What Google has done is illegal under EU anti-trust rules. It denied other companies the chance to compete on the merits and to innovate. And most importantly, it denied European consumers a genuine choice of services and the full benefits of innovation."
Google also faces EU fines over its AdSense advertising system and its Android mobile operating system.
In February, the Competition Commission of India hit the company with a fine of 135.86 crore rupees (about US$21.1 million) for "abusing its dominant position in online general Web search and Web search advertising services in India".
Google and other big multinational technology companies are also under pressure over alleged tax evasion, with the European Commission, the executive arm of the EU, recently unveiling a proposal to tax these companies at a rate of 3% as an interim measure.
Photo: courtesy European Union