China has banned the sale and import of coal with high ash or sulfur content in a move to promote cleaner coal and improve the nation's air quality.

Coal with ash content of more than 40 per cent and sulfur of more than 3 per cent are banned from sale and import into China starting 1 January, according to a regulation posted on the website of the National Development and Reform Commission.

Air pollution has become a huge issue in China's major cities. Credit:AFP

Lignite containing ash of more than 30 per cent and sulfur of more than 1.5 per cent is also prohibited.

China, the world's largest consumer of coal, is restricting the dirtiest grades to fight pollution.