Joaquin Almunia said in a speech that the EU investigation is still at an early stage but that officials were aware of the "importance of search to a competitive online marketplace."

He appeared to accept Google's arguments that it is hard to behave as a monopoly on the web, saying the fluid nature of the Internet may make it more difficult for powerful companies to elbow out other companies in new markets.

British price comparison site Foundem and French legal search engine ejustice.fr complained to the EU that they were ranked low in Google searches, claiming that this may be because they offer rival services to Google.

Google says its search results are entirely controlled by algorithms that demote sites with little useful content for users.

Low rankings matter because a higher ranking in a Google search drives higher volumes of traffic to Web sites.