SAN FRANCISCO - The Federal Trade Commission has turned to a former prosecutor in the Oklahoma City bombing trial to help run its antitrust investigation of Google Inc, escalating the stakes in the months-long probe into whether the Internet giant promotes search results that favor its business.

FTC Chairman Jon Leibowitz said on Thursday his agency had enlisted former Justice Department prosecutor and noted litigator Beth Wilkinson, best known for convicting Oklahoma City bomber Timothy McVeigh and now a partner with Paul, Weiss, Rifkind, Wharton & Garrison.

Wilkinson begins work on Monday in a case that could have significant implications for not just Google's growth ambitions but also consumers' use of the Internet.

"It certainly could be a significant step toward bringing an enforcement action when outside firepower is brought in," said Jeffrey Schmidt, a former FTC director of competition and now at law firm Linklaters.

Google has been accused of using its clout in the search market to stomp rivals as it moves into related Web businesses such as travel search. European regulators are also looking into similar claims.

The US agency has not yet decided whether to bring a lawsuit against the world's No. 1 search engine, Leibowitz , told a group of reporters during a trip to San Francisco and Silicon Valley.

But history suggests the hiring of Wilkinson increases the chances of litigation.

The last two times that the FTC hired an outsider to direct a specific case, both in 2008, the agency did take more aggressive action. In one case, it filed an administrative complaint that scuttled an acquisition by Inova Health System Foundation, and in the other it sued Cephalon Inc over deals that delayed the introduction of generic drugs.