China's Great Wall Motor said on Thursday it had filed a report with the country's regulators against BYD alleging that the electric vehicle giant's two top-selling hybrid models did not meet emissions standards.
It is a rare, public accusation from Great Wall Motor that has pulled the two companies into an open fight.
In a statement on its WeChat account, Hebei-based Great Wall Motor said documents were submitted on April 11 to the ecology and environment ministry, the industry and information ministry and the top market regulator that allege BYD failed to meet pollutant emissions standards in two hybrids.
BYD said in response that its products were compliant with China's standards
"We firmly oppose any kind of unfair competitive behaviours and reserve the right to sue," BYD said.
According to the documents, which Reuters has seen, Great Wall Motor accused BYD of using non-pressurised fuel tanks in its Qin Plus and Song Plus plug-in hybrids, which let the liquid inside evaporate more than in high-pressure tanks. It did not provide any evidence for its allegations.
Tank pressurisation is an issue for plug-in hybrids because they are designed to run on electric power alone at times, meaning fuel remains in the tank longer than it would for a normal internal combustion-engine vehicle.