In what has the appearance of a high-stakes, corporate sumo wrestling match, the Federal Trade Commission is reportedly investigating a hefty ad rate increase with which Google stung Microsoft. The investigation is said to be part of the FTC’s antitrust probe of Google that’s been going on for months.

Business Week reports a Microsoft spokesperson says Google has pursued practices that restrict competition and innovation. The complaint originated back in 2007, when Google began charging Microsoft $5 per click of Windows Live ads next to “hotmail” search results rather than the previous rate of 10 cents. Microsoft said it’s one of several companies subpoenaed by the FTC about the issue.

Google said it wasn’t aware of Microsoft’s specific allegations, and that relevance to searches is a factor that determines rates.

Google Ad Rate for Microsoft Said to Be Under U.S. Investigation [Business Week]

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