The European Commission has launched a formal antitrust probe into Google, following complaints from rivals that the search giant has abused its power.
"The Commission will investigate whether Google has abused a dominant market position in online search by allegedly lowering the ranking of unpaid search results of competing services," commisioners announced in a statement.
The investigation follows complaints from rivals including UK-based price comparison site Foundem and French legal search engine ejustice.fr, which allege that the company demoted matches from their sites in its unpaid search results.
Microsoft-owned German shopping site Ciao Bing has also complained to the Commission about Google's standard terms and conditions.
Commissioners will be scrutinising claims that Google has prevented partners from placing certain types of advertising on rival sites by the use of exclusivity clauses.
"Since we started Google we have worked hard to do the right thing by our users and our industry," the search giant responded in a statement.
"But there's always going to be room for improvement, and so we'll be working with the Commission to address any concerns."