Emissions from motor vehicles have become the major source of air pollution in China as the country remains the world's biggest auto producer and consumer for the past six years, according to a report issued by the Ministry of Environmental Protection.

The annual report on prevention and control of vehicle pollution said pollutants generated by motor vehicles across the country in 2014 totaled 45.5 million tons, a decrease of 0.5 percent from 2013.

Cars contributed most, discharging over 90 percent of the nitrogen oxide and particulate matter, major contributors to haze and smog.

In 2014, total vehicle sales in China reached almost 23.5 million units, continuing the trend of robust growth, the report stated.

It also noted that the number of cars owned by Chinese citizens jumped to 245 million in 2014, 33 times the ownership figures of 1980. So-called "yellow-label" cars, or heavily polluting vehicles, accounted for 6.8 percent.

Wang Jian, deputy director of the Department of Pollution Prevention and Control under the Ministry of Environmental Protection, said emissions resulting from rapid growth in the number of vehicles in China are compounded by combined pollution from coal smoke and vehicle emissions.

The official added that China has implemented a series of measures to control vehicle emissions, such as enhancing fuel quality and accelerating the pace of eliminating heavily polluting cars.

The ministry plans to introduce a total nitrogen oxide cap and strengthen supervision over the manufacturing, use and elimination of highly polluting vehicles.