Chinese economic growth decelerated to a 25-year low of 6.9 percent in 2015, down from 7.3 percent in 2014, according to data released on Tuesday by the National Bureau of Statistics.

Wang Bao'an, director of China's National Bureau of Statistics, commented: "It is really not a low speed. It is perfectly in line with a variety of factors constraining China's economic growth at this stage, and the needs of strategic objectives."

Facing questions about the authenticity of China's GDP growth data raised by some media and research institutions in the past year, Wang confirmed that the 6.9 percent rate in 2015 is a reliable statistic.

According to Wang, four facets of China's GDP accounting system support the authenticity of the data.

Firstly, Chinese GDP accounting uses solid and accurate base data, which is supported by a reliable system. The system consists of one million companies, directly linked to the network reporting system of China's National Bureau of Statics. This method prevents intervention and modification of the data. This is a very important guarantee for the accounting system.

Secondly, the National Bureau of Statistics has an investigation team of more than 20,000 people who directly conduct the survey and verify data. Meanwhile, the National Bureau of Statistics also cooperates with big data enterprises. In addition, the bureau holds an economic census every five years, which provides detailed statistical data of economic and social development nationwide.

Thirdly, the bureau has adopted internationally accepted methodology for GDP accounting. Last year, China formally adopted the SDDS standard of the IMF.

Last, China's statistics, especially for GDP accounting, have been recognized by international institutions including the United Nations Statistical Commission, the IMF and the World Bank.