Rural couples in Shanghai, Tianjin and five provinces have been entitled to have a second child if either of them is the only child of their families, the country's deputy population planning chief and a lawmaker confirmed on Tuesday.

"As per changes in demographic, economic and social landscapes, we have improved our policies regarding child bearing in recent years," Wang Pei'an, vice-minister of the National Population and Family Planning Commission, said on the sidelines of the ongoing session of the National People's Congress, which opened on Tuesday in Beijing.

In his Government Work Report at the opening of the legislature's annual meeting on Tuesday morning, Premier Wen Jiabao vowed to "progressively improve the government population policy" and "adhere to the basic State policy on family planning".

The State policy, instigated three decades ago, is not tantamount to a "one-child" policy, said Ma Xu, a national legislator.

Already, rural families can have a second child if the firstborn is a girl, and both rural and urban couples can have a second child if they are both the only child of their families.

Rural couples in Liaoning, Jilin, Jiangsu, Anhui and Fujian provinces then joined their rural cousins in Shanghai and Tianjin municipalities by being allowed to give birth to a second child if a husband or wife is an only child, they said.

The arrangement, not widely reported, took effect at least one year ago, according to Ma Xu, also director of the commission's Science and Technology Institute.

"It indicates the government has been fine-tuning the State policy on family planning," he told China Daily.

The legislator said it is the right time to further optimize the policy.

The number of people aged between 19 and 59 declined by 3.45 million year-on-year in 2012 on the Chinese mainland, making a significant dent in China's labor force.

The number of people aged 60 and older is estimated to top 200 million in 2013, according to a report on the aging population released by the Chinese Academy of Social Sciences on Feb 26.

There are changes in the size, structure and geographical distribution of the country's population, so the policy should improve to match the changes, the lawmaker said.

Had the country's family planning policy not been in place, China's population would be at least 400 million larger, he said. Given the sheer size of the current population, China should continue to stick to the basic family planning policy and stabilize the low birthrate, he added.

"We may consider extending the second-child policy now in place in the rural parts of seven regions including Shanghai and Tianjin to urban regions as well," he suggested.

Liu Dajun, a political adviser, agreed with Ma. The member of the National Committee of the Chinese People's Political Consultative Conference said China's population will start to decline in 2030 under the current policy.

"We have missed the best time to roll out the policy of allowing one couple to have two children. For the future of our country, we call for immediate action in adjusting the family planning policy," Liu said in a proposal submitted to the national committee.