The EU watchdog opened a probe into the world's most popular search engine in November 2010 after rivals, including Microsoft , accused Google of manipulating search results and promoting its own services while demoting theirs.

TripAdvisor competes with Google's online service Place, which aims to help consumers search for local businesses. It took its grievance to the Commission on Monday.

"TripAdvisor filed a complaint with the European Commission to address anti-competitive and unfair practices by Google that harm the marketplace and consumer welfare," the company said in a statement. "We hope that the Commission takes prompt corrective action."

In a two-paragraph statement, TripAdvisor gave no details of the specifics of its complaint or of how it believed it was being harmed.

Google said it was working closely with the Commission to explain how its business works.

"We haven't seen this complaint yet, but we will continue to discuss any concerns with the Commission, knowing that there's always room for improvement," Al Verney, Google's spokesman, said in a statement.

TripAdvisor's complaint brings the total number of cases before the EU watchdog to 14. Online travel agency Expedia, which spun off TripAdvisor last year, filed a complaint against Google with the EU Commission last week.

The majority of complainants are small competitors across Europe. Google has denied that it stifles competition. U.S. enforcers are also investigating Google, which controls more than two-thirds of the global search market.

EU Competition Commissioner Joaquin Almunia said last month he would decide whether to formally charge Google after Easter on April 8 or drop the investigation which began in 2010.

In separate investigations, EU privacy regulators are scrutinising Google's new privacy policy, which came into effect on March 1.

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