The European Union has opened an investigation into whether solar panels are being sold by Chinese firms below the cost of production, drawing an immediate protest from Beijing.

The EU said Thursday it launched the anti-dumping probe after a group of more than 20 European solar panel makers presented evidence that the Chinese products had “substantial adverse effects” on the industry.

China's Ministry of Commerce quickly issued a statement expressing “deep regret” at the investigation, warning that restrictions on China's solar panel products could hurt the global clean energy sector.

Beijing has denied providing illegal subsidies to Chinese solar power makers, a move that some say would give them an unfair edge over competitors on the international market.

In May, the United States imposed tariffs on several Chinese solar panel manufacturers, claiming they were illegally selling their products below cost.

The European action is the biggest ever anti-dumping claim filed with the EU. More than 60 percent of China's $36 billion in solar panel exports went to Europe last year.