BEIJING — China should further ease population controls by lowering one of the world’s highest marriage ages to encourage more births as the nation grows old, according to a lawmaker.

Huang Xihua, a member of the National People’s Congress, proposes cutting the minimum marriage age to 18 for both sexes and shifting policy to encourage more children. Under current law, men must be 22 to marry and women must be 20.

“The high marriageable age limit was introduced with the population controls,” Huang said, adding that the change will protect young couples in de facto marriages as well as their children, who can’t obtain the hukou residency registrations required to access many social services under existing regulations. “Now we have already allowed two babies, and we should give that choice back to people.”

More than 30 years of social engineering under the one-child policy has left the China with too few young people to support an aging society, fueling the risk of rising labor costs, lost competitiveness, and an overburdened social welfare system. China moved to address the situation in 2015 by allowing couples to have two children, yet the births still fell short of expectations.

After loosening the policy, officials estimated an increase of 4 million additional births a year through 2020. The 2016 rise was less than half that amount.