The simmering trade war between the US and China over renewable energy policy intensified yesterday, as Chinese officials accused the US of violating World Trade Organisation (WTO) rules through its support for clean technologies.

According to state news agency Xinhua, the Chinese Ministry of Commerce (MOC) has completed an investigation that concluded six US renewable energy programmes are in breach of article three of the Agreement on Subsidies and Countervailing Measures, as well as article three of the General Agreement on Tariffs and Trade.

The six support schemes for wind, solar and hydropower are in operation in Washington, Massachusetts, Ohio, New Jersey and California, and according to the MOC are hampering exports of Chinese goods and do not represent “fair treatment” for Chinese firms.

The investigation raises the prospect of legal action against the US by the Chinese government if the schemes are not removed.

The latest threat of WTO complaints is part of an increasingly complex trade dispute, initially sparked by a US Commerce Department investigation into support for Chinese solar panel manufacturers, which culminated this May in the introduction of import duties on Chinese solar cells.

The EU is similarly investigating Chinese renewable energy policies after complaints from Western manufacturers of solar and wind energy technologies that they are struggling to compete with heavily subsidised Chinese firms.

However, Chinese officials have maintained that their support mechanisms for clean tech firms are in compliance with WTO rules, are largely similar to those already operated in industrialised countries, and are part of efforts to curb greenhouse gas emissions in line with its commitments under international climate change agreements.

The government has repeatedly signalled that if the US and others file formal complaints against China’s renewable energy policies it will retaliate with similar complaints against similar schemes adopted by its trading partners.