ING Direct has filed a lawsuit alleging that Discover Financial Services has copied the orange sphere designs used in its advertisements and Web pages.

ING Direct, the U.S. online banking unit of the Dutch financial company ING Group NV, said it is the only company that is allowed to use circular, orange logos to market financial services in the United States, according to a trademark-infringement lawsuit filed last week in U.S. District Court for the District of Delaware.

"Defendants have profited from their unlawful actions and have been unjustly enriched to the detriment of ING Direct," and have backtracked on a pledge to limit its use of the distinctive design, the banking company said in the complaint.

ING Direct filed a trademark application for the orange-ball logo in 2000. Since then orange has become the predominant color of its Web site, retail banking locations, and advertisements, according to the court filing.

The lender filed a similar lawsuit in October against PNC Financial Services Group Inc.

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