Concerns about the sustainability of China's employee pension program have stirred among experts as Premier Li Keqiang in late October said more than 38 million employees failed to pay contributions.

Shen Shuguang，a social security expert from Sun Yat-sen University in Guangzhou, said some workers have decided to stop topping up pension contributions as they have made contributions for 15 years, the minimum period to be eligible to claim pension, China Times reported on Thursday.

Shen said three other types of people failed to pay contributions: laid-off workers, migrant workers and employees from small businesses that are struggling in the economic slowdown.

Tang Jun, a researcher who specializes in social policies at the Chinese Academy of Social Sciences, told the newspaper that the current worry will create problems for the country's employee pension program.

At the 16th National Congress of the All-China Federation of Trade Unions on Oct 21, Premier Li said about 300 million employees had joined the state employee pension program but more than 10 percent of them did not pay their pension contributions.