An investigation has been opened by the US Department of Justice into a possible breach of antitrust laws after Yahoo! announced Google Adsense would be implemented in limited trials on Yahoo! search results, in an effort to scupper Microsofts hostile ultimatum to accept a $44.6bn takeover bid.

Concerns were raised by regulators after a telephone call between Google’s Eric Schmidt, and Yahoo!’s Jerry Yang, where Google CEO Schmidt allegedly offered to help search rival, Yahoo! defeat the strong-arm tactics of Microsoft with the proposed Adsense partnership, increasing Yahoo!’s bargaining leverage against Microsoft.

While the Yahoo/Adsense trials were penned for only 2 weeks, investigators are concerned about a possible longer-term partnership between the search rivals, and the anti-competitive implications that could arise. A claim strongly refuted by Yahoo’s Tracy Schmaler, who said..

“Yahoo proactively kept the Department of Justice informed of its intention to conduct this limited test with Google and has provided information to DOJ on the nature of the test…”

..in a rebuttal which was mirrored by a Google spokesman, who added..

“We informed the Justice Department before we launched this test, and we have been responsive to their questions about it.”

Antitrust regulators are said to be keeping a keen eye on any possible Google/Yahoo partnership which could be indicative of anti-competitive practices in much the same way as the proposed Microsoft/Yahoo merger. Both deals are as yet unconfirmed but already raising eyebrows in the DOJ.

See Also: Microsoft eyes Yahoo! for $44bn buyout, Ballmer furious as Yahoo! trials Google Adsense