China's decision to dump its notorious one-child policy will not significantly increase the country's low fertility rate, a leading state-run thinktank has said, reinforcing reports that Chinese couples were reluctant to have two children due to high cost of living.

The "two-child policy" might cause fluctuations in the birthrate, but will not incite a significant rebound, the Institute of Population and Labour Economics of the Chinese Academy of Social Sciences has said in a report.

It said the Chinese couples' willingness to have a second child was "not high," so fewer couples will take action following the policy change. While couples of child-bearing age will take time to consider and may eventually have a baby, state-run Global Times reported.

In July, an online survey of 8,491 respondents conducted by portal sohu.Com reported that only 36 per cent were willing to have a second child.

Mu Guangzong, a professor at Peking University's Institute of Population Research, agreed with the report.

Lifting the ban on second children only grants couples the right to have a second baby, but their physical capability and willingness to have a second baby will ultimately determine the birthrate, Mu said.

Mu said couples born in the 70s have missed the best age for childbearing, while not many born after 1980 have a strong desire to have a second baby, leading to a low birthrate.

In addition to grant permission for a second child, the government should also offer incentives such as rewards and subsidies to encourage all eligible couples to take advantage of the new policy, said Mu.

"People will not have a baby until they are assured they can afford to raise one," Ma Li, director of China Population and Development Research Centre -- a think tank associated with state-run National Health and Family Planning Commission -- told the daily.

However, even if China, the world's most populous nation, encourages child-bearing, any increase in the birthrate will be limited as global precedents suggest the fertility rate will not rebound sharply when it is lower than 1.5, the report said.

According to experts, China's fertility rate has lingered at 1.5 children per woman of childbearing age for the past few years.

A draft amendment to the Population and Family Planning Law allowing all couples in China to have a second child was approved by the State Council yesterday and will be handed over to the country's top legislator for review soon.

The policy is aimed at improving the population structure to address future labour shortages.