The European Commission has opened an antitrust investigation into allegations that Google has abused its search-engine dominance by down ranking competitors in the results it delivers. The original complaint was brought against Google earlier this year by three companies – British price comparison site Foundem, French legal search site eJustice, and a German price comparison site owned by Microsoft known as Ciao – and has since expanded to look into other issues such as how the company deals with advertising partners and the way it tracks ad campaign data.

In its defense, Google says that there are good reasons why certain sites are ranked poorly in search results. For example, Foundem, one of the sites that filed the original complaint is badly ranked because it "duplicates 79% of its website content from other sites," and Google has openly warned webmasters that their algorithms penalize duplicate sites. With regards to its core online advertising business the company said that they already allow customers to take their data with them when switching to a rival advertising platform and that its contracts have never been exclusive.

Nevertheless, Google says it will cooperate with the investigation. For its part the Commission stressed that opening the investigation does not imply that it already has proof of any infringements, merely that it is looking for it.