Barnes & Noble has accused Microsoft of misusing patent law to thwart rivals to its Windows Phone 7 business by requiring them to pay "pay exorbitant licensing fees or face protracted and expensive patent infringement litigation."

The charges come in a response filed in a case Microsoft brought against Barnes & Noble last month before International Trade Commission and the U.S. District Court of the Western District of Washington. Microsoft alleged that Barnes & Noble's Nook e-reader violates its patents covering the way users tab through various screens to find the information they're after, as well as the way they interact with documents and e-books.

The Nook Color, a target of Microsoft&39's lawsuit.

The suit is part of Microsoft's broader campaign against Google's Android operating system, which the Nook runs. Microsoft also named Foxconn International Holdings and Inventec Corporation as defendants in the case.

In its filing, Barnes & Noble accuses Microsoft of asserting patent claims over "arbitrary, outmoded, or non-essential design features." The filing, first reported by All About Microsoft blogger Mary Jo Foley, accuses Microsoft of abusing the patent system to hinder competition.

"Microsoft is misusing these patents as part of a scheme to try to eliminate or marginalize the competition to its own Windows Phone 7 mobile device operating system posed by the open source Android operating system and other open-source operating systems," Barnes & Noble alleges in its response. "Microsoft's conduct directly harms both competition for and consumers of eReaders, smartphones, tablet computers and other mobile electronic devices, and renders Microsoft's patents unenforceable."

For its part, Microsoft suggests that Barnes & Noble is diverting attention from the allegations of patent infringement.

"Our lawsuits against Barnes & Noble, Foxconn, and Inventec are founded upon their actions, and the issue is their infringement of our intellectual property rights," the company said in a statement. "In seeking to protect our intellectual property, we are doing what any other company in our situation would do."