Microsoft throws weight behind EU's Google probe

Google has long pointed to Microsoft's involvement in the probe, since one of the original complainants, online shopping site Ciao, is owned by Microsoft's search engine Bing. Another company involved in the case, U.K.-based price comparison site Foundem, is a member of a Microsoft-sponsored innovation organization.

"For our part, we continue to discuss the case with the European Commission and we're happy to explain to anyone how our business works," Verney said.

Smith as well said that Google blocked Microsoft's Windows Phones "from operating properly with YouTube," nevertheless offers better services to its own Android phones and iPhones, whose producer Apple Inc. does not own a search engine.

Way of closing in on Google

Yet neither Bing nor Yahoo have found a way of closing in on Google, which processes two out of three online searches in the U.S. In Europe, the Mountain View, Calif.,-based company controls more than 90 percent of the search market. The two companies as well compete in other areas, just as cloud computing - where they offer remote server space and software processing to customers.

Central to Thursday's complaint is how Google's practices affect advertising - the main source of revenue for Web companies offering free services.

If Google is found guilty of anticompetitive behavior it could be fined up to 10 percent of annual revenue, which reached some $29 billion last year.