An assertion by a US-based academic that China will be home to the world's largest Christian congregation by 2030 is inflated and not rooted in fact, said officials close to religious affairs authorities.

"The estimate is unscientific and obviously an exaggeration. China advocates religious freedom and we are not against people's right to believe in any religion. In this respect, an estimate of the number of Christians makes little sense," an official told the Global Times on condition of anonymity.

The Christian community in China is estimated to grow to 160 million by 2025 and the figure will exceed 247 million by 2030, according to Yang Fenggang, director of the Center on Religion and Chinese Society at Purdue University in Indiana.

Yang told the Global Times via e-mail Thursday that his conclusions are based on annual growth rate calculated by available figures, and the result is only the probability of future growth trends, rather than an absolute certainty.

"Based on the Pew Research Center's Report of Global Christianity, the Christian population in China took up some 5 percent of total population in 2010 [67 million], while it is widely recognized that there were 3 million Catholics and 3 million Protestants around 1980, which would make an annual growth rate of around 10 percent," Yang said.

Yang added that he used a lower growth rate by counting in statistics from 1950 to 2010 when there were restrictions on religious activity during the Cultural Revolution (1966-76).

There were only 1 million Protestants and 3 million Catholics in 1949, he claimed. China's population was approximately 541 million at that period of time.

He pointed out that official statistics are often underestimated, but the development of Christianity in China is often exaggerated by the authorities, which has resulted in many strict yet unnecessary restrictions and may turn out to be contrary to maintaining social stability.

"Scientific studies must be in line with the truth without over or underestimations to mislead senior officials as well as the public," Yang noted.

In 2010, the Chinese Academy of Social Sciences (CASS) put the number of Protestants at some 23 million, according to a survey on religion in China. The figure was about 1.8 percent of the total population.

Another report from the Institute of Social Science Survey at Peking University showed that the percentage rose slightly to 1.9 percent in 2012, indicating 26 million Protestants in China.

Shen Guiping, a religious studies expert at the Central Institute of Socialism, told the Global Times previously that Yang and Pew's estimates may not be accurate, as they have made a looser definition of who is a practicing Christian.

CASS usually identifies Christians if they attend religious activities weekly, Shen said, while the other estimates may have taken other elements into account, such as attendance at illegal religious activities.

"Those estimates reflect that research fellows or institutes intend to encourage the development of Christianity in China," Shen said.