A group of seven U.S. solar cells and panels makers on Wednesday petitioned the U.S. government to stop what they say is a rising tide of heavily subsidized product entering the American market from China's state-supported solar industry.

The Coalition for American Solar Manufacturing today filed complaints with the U.S. Department of Commerce and International Trade Commission seeking relief from what they claim are illegal Chinese trade practices, according to a statement from Hillsboro, Oregon-based SolarWorld Industries America Inc., the U.S. division of Germany's SolarWorld and the company leading the charges.

SolarWorld noted that the cases are among the largest against China and in the renewable-energy industry history. The cases allege massive subsidies and dumping margins exceeding 100 percent.

Among the complaints are claims that the Chinese government provided heavy subsidies to advance its pricing and export aggression, increased production for export markets as they impeded imports and sidestepped U.S. manufacturing standards for labor, quality and the environment.

Artificially low-priced solar products from China are crippling the domestic industry, said Gordon Brinser, president of SolarWorld Industries America.

China's systematic campaign to dismantle the U.S. industry has cost thousands of jobs in Arizona, California, Maryland, Massachusetts, New York and Pennsylvania, Brinser added.

According to the SolarWorld statement, imports of Chinese crystalline solar cells and panels rose by more than 300 percent from 2008 to 2010, with July 2011 volumes exceeding that of 2010 and imports within the first eight months of the year totaling $1.6 billion.

In the past 18 months, seven U.S. companies have had to downsize or shut down operations, it added.