The registration system, introduced in the 1950s to curb population growth in cities, gives urban and rural residents widely differing social welfare entitlements. Access to benefits also varies greatly between cities, depending on their regional economic development.

About 57 per cent of survey respondents said the system was important in getting their children into city schools, while more than a third said it was useful in accessing medical and unemployment insurance. Nearly 19 per cent of respondents said registration was needed if they wanted to buy houses or cars, while 18 per cent said it increased job opportunities.

Dang Guoying, of the Chinese Academy of Social Sciences, told the China Youth Daily that a Beijing citizen earning less than 2,500 yuan a year could receive monthly subsidies as well as medical insurance, a pension and even low-cost housing. That was in contrast to the few benefits given to farmers living on the same income.

Duan Chengrong, a population expert from Renmin University in Beijing, said it would be difficult for big cities such as Beijing and Shanghai to change because they could not afford benefits for a large number of migrant workers.

Some regions have sought to change the scheme to help narrow the urban-rural divide, but have found problems. Guangdong had to suspend its attempts to unify registrations just six months after announcing the plan in 2001, and Zhengzhou, in Henan province, made a similar decision in 2003, saying an increase in population meant the change was too heavy a burden for the city, the China Youth Daily reported.

But Professor Duan said the registration system was an obstacle to the market economy and the trend was towards eliminating it.