China Daily reported experts blamed the gender gap with males outnumbering females for such ills as the rising crime rate, growing demand for pornography and illegal marriages.

Xinhua news agency said there are about 18 million more males than females between the ages of 20 and 25 and the gap was expected to widen to 30 million by 2020.

Jiang Chunyun, director of the non-governmental China Family Planning Association, said 119 boys are born for every 100 girls in the country. That compares with the international average ratio of 103-107 boys for every 100 girls.

The head of the National Population and Family Planning Commission was quoted by China Daily as saying the gender imbalance has been evident since the 1980s, saddling China with the world's most serious gender discrepancy.

Some experts blame the problem on the society’s traditional preference for male heirs, gender testing of fetuses with ultrasound and backward social security scheme in rural areas, the report said.