Two lawmakers on Monday asked the Federal Trade Commission to investigate whether Google's search results violate antitrust law.

Senators Herb Kohl (D-Wisc.) and Mike Lee (R- Utah) sent the FTC a letter urging it to probe allegations that Google unfairly gives its own products and services a high placement in the search results. “Google's critics argue that ... Google has a strong incentive to bias its search results in favor of its own offerings. Rather than act as an honest broker of unbiased search results, Google's search results appear to favor the company's own web products and services,” the lawmakers write.

The lawmakers referred in their letter to a recent Senate hearing at which Yelp CEO Jeremy Stoppelman lambasted Google for returning Yelp reviews in the local search results without a license. "Google forces review Web sites to provide their content for free to benefit Google's own competing product -- not consumers," Stoppelman said in his written statement. "Google then gives its own product preferential treatment in Google search results."

Google CEO Eric Schmidt testified at the hearing that Google is “in the rankings business.” He said that while he has sympathy for businesses when their placement in the organic results drop, such changes are inherent to search engines.

The lawmakers say they aren't taking a position on whether Google is violating antitrust laws, but contend that “the allegations regarding Google's search engine practices raise important competition issues.”