The 2011 Fukushima quake destroyed factories and disrupted auto supply chains for months, raising questions about whether production should go overseas.

A decade later, Japan's heavy reliance on coal and gas to generate electricity means that unless it can replace them with renewable energy sources, carmakers would emit carbon during production that could put it over limits other countries adopt, even for zero-emission vehicles, said Akio Toyoda, speaking as chairman of the Japan Automobile Manufacturers Association (JAMA).

"In the past, production was moved out of Japan to the markets where cars were sold or to lower wage locations that gave a competitive advantage. The next shift could be to countries that have a more sustainable energy structure," Toyoda said.

"The challenge is an order of magnitude greater than the quake was," he added, speaking on the tenth anniversary of the quake and tsunami that destroyed towns and factories and claimed 20,000 lives.

Of the nearly 10 million cars built in Japan by Toyota, Honda Motor Co, Nissan Motor Co and other manufacturers, around half are exported, according to JAMA.

The industry employs more than 5 million people and Japan's car lobby can influence government policy. Toyoda's warning comes as Prime Minister Yoshihide Suga's administration considers how to achieve a target it announced last year to eliminate greenhouse gases emission by 2050.

Japan has become more reliant on coal and natural gas since the tsunami as the destruction of the Fukushima nuclear plant forced the shutdown of other reactors.

In addition to an expansion of solar energy, Japan's government and Toyota are also promoting the use of hydrogen fuel as a way to lower carbon emissions.

(Reporting by Tim Kelly; editing by Richard Pullin)