An academic study from Harvard and Columbia universities — and funded by Google competitor Yelp — found that Google discriminates against competitors in its search results.
The study showed that Google favors search results that direct users to Google content over results that point to competitors such as Yelp and Orbitz, according to one of the lead researchers, Tim Wu.
"What the data shows, is in the interest of anti-competitive behavior, maybe they're hurting consumers along the way," Wu said. "It puts the grist in the mill for an antitrust enforcer."
Google did not respond to a request for comment, but a spokesperson said in an April blog post that rival businesses appeared to be thriving, writing "people have more choice than ever before."
European investigators have been at work since April trying to determine whether Google distorts search results for its own benefit, pushing out rivals in the process.
However, a similar inquiry by the U.S. Federal Trade Commission into possible antitrust violations was dropped in 2013.
Yelp said the new report, which it presented to European regulators Friday, could put pressure on the investigation and encourage additional research.
"We believe these revelations are timely given the active inquiries into these very issues by antitrust authorities," said Luther Lowe, Yelp's vice president of public policy.
But others said the report wouldn't prompt serious action, saying it did not prove a deliberate effort by Google to harm its rivals.
"I think hyperbole has gotten ahead of the fact," said David Balto, an antitrust lawyer in Washington and former policy director for the FTC. "There's a long journey to take before anyone can say this violates the competition laws."
The research by Yelp instead appeared to be an attempt to "hobble" Google, he said, forcing the company to spend time and money justifying its conduct.
To conduct the study, Wu and Michael Luca of the Harvard Business School, working alongside Yelp's Data Science Team, set up two search engine scenarios.
One was the typical experience on Google.com, which calls up a box listing local businesses and their addresses, which are marked on an accompanying map. The links lead to information from Google+.
The alternative mimics Google.com — but orders Google to search a variety of review websites such as Yelp, Orbitz, TripAdvisor and FourSquare.
Searching "pediatrician nyc," for example, led to a list of 31 review links on the traditional Google site, but 719 on the alternative version.
Testing 2,690 participants, researchers found users were 45% more likely to engage with items pulled up by the alternative site with its broader focus, rather than the traditional site with Google listings. This suggested to researchers that Google's findings weren't necessarily better than other options.
"Google is making a strategic choice to display their own content, rather than choosing results that consumers would prefer," states the study.
The researchers said their study will appear in the Journal of Antitrust Enforcement from Oxford University Press.