The top antitrust official at the U.S. Justice Department last month backed Microsoft
by urging state prosecutors to reject a confidential complaint filed by Google, The New York Times reported on Sunday.
Google accused Microsoft of designing its Vista operating system to discourage use of Google's desktop search program, lawyers involved in the case told the Times.
The complaint, which is tied to a consent decree that monitors Microsoft's behavior, has not been made public by Google or the judge overseeing the consent decree, the article said.
State officials told the newspaper that a memo by Thomas Barnett, an assistant attorney general, rejected the Google complaint, repeating legal arguments made by Microsoft.
The article said the memo was sent to state attorneys general around the United States and alarmed many of them, with some state officials saying they believed Google's complaint had merit.
The New York Times said the action demonstrates that nearly a decade after the U.S. government began its landmark effort to break up Microsoft, the Bush administration has changed course by defending the company against accusations of anti-competitive conduct.
Bradford Smith, the general counsel at Microsoft, told the Times that the company was unaware of the memo. He told the newspaper that Microsoft had not violated the consent decree and that it had already made modifications to Vista in response to concerns raised by Google and other companies.
Microsoft, Google and the Justice Department could not immediately be reached for comment.
The judge overseeing the consent decree is Colleen Kollar-Kotelly of the Federal District Court in Washington.