China still faces a tough challenge to redress a long-term skewed sex ratio of births on the mainland, which now stands at about 117.7 boys for every 100 girls, said Chen Zhu, vice-chairman of the 12th National People's Congress Standing Committee.

He made the remark at an awareness-raising event on gender equality and women's empowerment, held on Friday by the National Health and Family Planning Commission.

The global norm is 103 to 107 boys for every 100 girls.

"Such a skewed ratio will undermine China's healthy and balanced population development in the long run and lead to great difficulty for men to find a wife," Chen said.

By 2020, there will be 30 million more Chinese males aged 20 to 45 than females of the same age, which will prompt a marriage squeeze, expert estimates show.

A marriage squeeze refers to a demographic imbalance in which the number of potential brides does not approximately equal the number of potential grooms.

"That might upset social stability and harmony," Chen warned.

The imbalance in China's sex ratio at birth has been gradually curbed largely due to government-led administrative measures and the difference has continued to decline on the mainland during the past four years, statistics from the commission showed.

It reached a record high of 121.2 boys for every 100 girls in 2004.

"But that still stands among the highest across the world given that the country has a deep-rooted tradition to prefer sons over daughters," Chen said.

To eliminate that, "more social and economic policies favoring girls will be introduced to gradually change the social norm where males are more preferred as they carry the family name and later support the parents," he said.

A comprehensive approach is needed to redress the skewed ratio, Chen urged.

In China, sex-selective abortions are deemed the direct cause of the imbalance, according to Lu Jiehua, a sociology professor at Peking University.

In response, a nationwide campaign to crack down on non-medical fetus sex determinations and sex-selective abortions has been launched by the commission, which has passed relevant regulations, previous reports said.

Doctors who are found to violate such regulations will face revocation of their licenses and the hospitals involved will also be penalized harshly.

"Such measures have to be institutionalized to sustain long-term efforts," Chen said.

Wang Pei'an, deputy director of the commission, agreed and called for participation and support from the general public to strive for gender equality.