Joaquin Almunia, the EU competition commissioner, said Google must offer concessions to allay the bloc's antitrust worries, The New York Times reported Wednesday.
Almunia, the bloc's top antitrust official, said he had written to Eric E. Schmidt, Google executive chairman, "asking Google to present better proposals, or improved proposals."
"I concluded that the proposals that Google sent to us months ago are not enough to overcome our concerns," he said.
Google controls more than 90 percent of the Internet search market in some European countries compared to about 70 percent in the United States.
European companies including publishers, mapping and travel firms have complained Google gives favored position to its own products in search results.
Google's proposals to date would still attract the vast majority of searchers to the company's own products and discourage them from visiting rivals, said Thomas Vinje, a spokesman for Fairsearch Europe, a group of Google's competitors.
Google has proposed labeling results that pointed to its own services, like Google Maps, as its own properties and separate them from general search results with a box.
It has also proposed that for specific industries like restaurants and hotels, Google would provide a menu of at least three options for non-Google search services.
Google's rivals have said they want a tougher set of rules.
"Google's proposed commitments across the board retard rather than promote competition," Vinje said.