Google initially submitted its proposed concessions to the European Commission in April. That proposal included the possibility of placing search results for from competing search engines alongside its own results.
But European Competition Commission Joaquin Almunia said at a press conference on Wednesday that Google must make better proposals if it wishes to reach a deal with the commission, according to Reuters.
"I concluded that the proposals that Google sent us are not enough to overcome our concerns, Almunia said.
Google's initial proposals, which didn't go far enough, would also have the company clearly label search results from its own properties, such as Google News and Google Shopping. The company also offered to block as much as 10 percent of its Web content from displaying in Google's search results.
The EU was compelled to investigate whether Google was using its search dominance to promote its own services ahead of competitors. Rival Microsoft was one of the primary complainants, but smaller players such as travel site Expedia, social review site Yelp and British shopping comparison site Foundem also joined the calls for an investigation.
If Google cannot satisfy the EU, the company could face a fine of as much as $5 billion. No deadline has been set, but Almunia indicated he'd like to reach a resolution by the end of the year.
Apple has been working to lessen its reliance on Google since the company started pushing its own Android mobile operating system to compete with Apple's iPhone. Late Apple co-founder Steve Jobs felt betrayed by Google.
Apple no longer uses Google Maps data for its native Maps application in iOS, and with this year's release of iOS 7, Microsoft's Bing will become the default search provider for voice-driven queries to its Siri personal assistant software.