China's coal consumption fell for the second year in a row, government data showed Monday, as the world's biggest polluter attempts to tackle chronic pollution that accompanied economic growth.

Coal use fell 3.7 percent last year compared to 2014 levels, according to a report from China's National Bureau of Statistics (NBS). The drop follows a 2.9 percent decrease in 2014.

China's rise to the world's second largest economy was largely powered by cheap, dirty coal. As growth slows, the country has had a difficult time weaning itself off the fuel, even as the pollution it causes wreaks havoc on the environment and public health.

China's consumption of the fuel doubled in the decade to 2014, reaching more than four billion tonnes a year.

Monday's figures did not give an absolute total.

It emerged in November that China had been under-reporting its consumption for years, after a different set of statistics were revised, with the figure for 2012 alone going up 17 percent, or 600 million tonnes.

There are widespread doubts over the accuracy of official statistics in China, which critics say can be subject to political manipulation.

Coal fell to 64 percent of the country's energy sources last year, Monday's NBS report said, down from 66 percent in 2014.

Observers reacted to the declines with tempered optimism.

"These statistics show that China is on track to far surpass its Paris climate targets, which is great news for everyone," said Lauri Myllyvirta, a senior global campaigner on coal for Greenpeace. "However, the trend is not moving as fast as it could."

The government plans to lay off about 1.8 million workers in the steel and coal industries, a human resources and social security ministry official said at a press briefing on Monday. Both sectors have long been plagued by overcapacity.

China's President Xi Jinping has said that the country's CO2 emissions, to which coal is a major contributor, will peak "around 2030", as pledged in Paris.

The State Council, China's cabinet, has also announced plans to reduce by 60 percent the amount of "major pollutants" coming from its coal-fired power plants by 2020.

Despite the decrease in coal use, many Chinese cities are often blanketed with toxic smog, much of it the result of using the fuel in industries like power generation and steel.

Nearly 300 Chinese cities failed to meet national standards for air quality last year, according to a Greenpeace report.