China has been experiencing the world's largest population flow, with the number of migrants doubled in the past 10 years, said Wang Guoqiang, deputy director of the commission.

More than 80 percent of migrants are rural people seeking jobs in cities, Wang told a national conference, noting that migrant workers would remain the majority of floating population for a long time.

Last year, China's migrant women of child-bearing age totaled 31.9 million. About 83 percent of newborn migrant babies registered in their hometown and were given birth certificates.

In Shanghai, where the conference on family planning for migrant population was held, one third of the total population or 5.81 million were from other places, according to statistics for last year.

Migrant workers eased Shanghai's shortage of labor force and the pressure of aging population, but meanwhile posed challenges to the city's public administration and services, especially birth control, said officials.

According to official figures, last year one third of Shanghai's newborns were in migrant families. Babies of migrant workers out of family planning accounted for 88 percent of the city's total unplanned births.

Birth control and other issues concerning migrant workers are crucial to China's overall family planning and the building of a new socialist countryside and a harmonious society, said Wang.

The commission has urged local governments to ensure funding and personnel for family planning and improve services for migrants, and cover the family planning of migrants in future urban public administration and service system.