Protests at more than 40 solar companies broke out as EU member states begin voting on proposed anti-dumping duties ranging from 37 percent to 68 percent Friday. The provisional rates will be effective from June 6 if the proposal is passed.

Representatives of three solar panel giants, Yingli Green Energy Holdings Co, Trina Solar Ltd and Canadian Solar Inc, held a press conference Thursday in Beijing, lashing out at the EU penalties and calling for free trade.

In a joint statement, the three said any market restrictive measures would hurt China's solar industry, but would also hinder solar application and development in Europe and have a major negative impact on the EU's economy and employment.

According to a research report by German consulting firm Prognos, the punitive duties could lead to job losses of more than 200,000 in Europe over three years.

Some 1,000 workers gathered at a Yingli factory compound in the city of Baoding in northern China's Hebei Province, holding signs of "No Trade Protection." Workers from other solar firms protested across the country.

Meng Xiangan, deputy director of China Renewable Energy Society, criticized the EU's move as trade protectionism and believed that China might take retaliatory measures.

Free trade, fair competition, opening-up and cooperation are the key prerequisites to the healthy development of the global PV industry, said Fan Ruifeng, public relations director of Trina Solar Ltd.

The protests came on the heels of an announcement Wednesday by the China Chamber of Commerce for Import and Export of Machinery and Electronic Products that the first-round of negotiations designed to ease the current solar panel trade spat between China and the EU by agreeing on an export price had failed.

At the EU's invitation, the chamber sent a negotiation team and put forward pragmatic price undertaking plans, but the EU side turned them down, refusing to answer questions from the Chinese side, said Wang Guiqing, deputy chief of the chamber.

The EU did not show any sincerity in tackling the problems, leading to a breakdown in talks, the agency said. Price undertaking basically means exporters raise the export cost of a product to avoid the possibility of an anti-dumping duty.

European PV firms have also lodged a separate complaint accusing their Chinese peers of receiving government subsidies that violate international trade rules.

The punitive duties, if imposed, could deal a heavy blow to China's already struggling PV industry as it relies on the European market, said Zhang Qian, government relations and business development director at Canadian Solar Inc.

China's PV exports to Europe slumped 45.1 percent year on year to $11.2 billion in 2012, but the value still accounted for nearly half of the country's total shipments, according to statistics from the chamber.

China's PV industry has boomed over the past decade, but is now struggling with excess capacity and weak market demand that has forced some small firms out of business and even put some giants on the brink of bankruptcy.

Worse still, leading solar panel maker Wuxi Suntech, a major subsidiary of the New York-listed Suntech Power based in the eastern Chinese city of Wuxi, declared bankruptcy in March.

China-made PV products would completely lose price competitiveness and EU's orders would be awarded to solar firms from Europe, the United States and even Taiwan, said Hou Wentao, an analyst with Guotai Junan Securities. China might increase domestic solar panel installations to help the industry hedge against the slumps in exports to Europe, added Hou.

"We should change the extensive growth mode and rely more on innovation and technology rather than on cheap labor and resources in grabbing market share and profits," said Meng of China Renewable Energy Society.

Some firms are eyeing emerging markets to help reduce their over-reliance on Europe. "We will consider exploring the African and Southeast Asian markets in a bid to reduce the risk posed by the excessive reliance on one single market," said Zhang of Canadian Solar Inc.

"Yingli is preparing for the worst. If the punitive duties are levied, we will move our plant to another country," said Wang Yiyu, Yingli's chief strategy officer. "But China's PV industry would then be struck down completely."