Microsoft Corp stepped up its legal battle with Motorola Inc on Tuesday, as the software company accused the phone maker of charging excessive royalties on network technology used in Microsoft's Xbox game system.

The suit, filed in federal court in Seattle, comes a month after Microsoft charged that its former ally Motorola infringed a number of its patents in its Android-based smartphones, which run on software built by Google Inc.

The latest suit alleges that Motorola breached its commitments to standards organizations that allow other companies to license its patents relating to wireless technology and video coding, which are used in Microsoft's Xbox gaming console.

According to Microsoft, Motorola demanded "royalties that are excessive and discriminatory," and asked the court for compensation from Motorola.

Motorola did not immediately return a call seeking comment.

The case is 2:10-cv-01823, complaint filed in the United States District Court for the Western District of Washington at Seattle.