Taiwanese solar stocks led by Motech Industries fell after the US proposed expanded penalties on solar energy imports in a victory for the US unit of SolarWorld, which accused mainland China of shifting production to Taiwan after it lost an earlier case. Motech, Taiwan's biggest solar-cell producer, slumped 6.9 per cent to NT$44.40 (HK$11.47), the biggest one-day drop since May 21 last year. Gintech Energy, E-Ton Solar Tech and Neo Solar Power also tumbled. The US Department of Commerce issued a preliminary finding last Friday that said overseas producers, including mainland China's Trina Solar and Taiwan's Gintech, sold goods in the US at unfairly low prices, a practice known as dumping. It called for duties ranging as high as 165 per cent for some mainland Chinese manufacturers and 44 per cent for those in Taiwan. China hopes the US can handle anti-dumping and anti-subsidy probes on mainland Chinese solar products "cautiously," its Ministry of Commerce said in a statement. The ministry, which called for a quick end to the probes, said an escalation will hurt industries in both countries. Jennifer Liang, a Taipei-based analyst at KGI Securities, said the duties were higher than the market expected. "The US accounted for about 30 per cent of Taiwanese solar-cell shipments in the past year and a half," she said. The duties will prompt Taiwanese producers to rely on Japanese and European markets more, she added. "We should not have to compete with dumped imports or the Chinese government," said Mukesh Dulani, the president of SolarWorld Industries America. The SolarWorld case has split the US solar-energy industry, with manufacturers seeking protections against being undercut by cheap imports, and installers pressing for low-cost equipment, regardless of origin. "We strongly urge the US and Chinese governments to 'freeze the playing field' and focus all efforts on finding a negotiated solution," said Rhone Resch, president of the Solar Energy Industries Association. A final decision by the commerce department will be made in mid-December. The independent US International Trade Commission will determine by the end of January whether US makers of the solar power goods were harmed by the imports. If so, the duties will be permanent. US imports from mainland China and Taiwan of the crystalline silicon photovoltaic cells, panels and modules used to make electricity from sunlight were valued at US$2.2 billion last year, according to the commerce department.