China's most populous province has asked for permission to ease the one-child policy after more than 30 years, an official said Tuesday, as concerns grow over gender imbalances and an ageing population.

Guangdong in southern China wants Beijing to allow couples where just one parent is an only child to have a second baby, according to a local government official who declined to be named.

China's one-child policy was introduced in 1979 to curb population growth in the nation of more than 1.3 billion people, but has become increasingly unpopular as the country's population ages.

Critics blame the policy for creating gender imbalances -- sex-specific abortions are common and female infanticide and the abandoning of baby girls have also been reported.

The policy also puts huge pressure on only children to support their parents and two sets of grandparents.

Policy violations usually result in hefty fines and a cut back in social services, although some ethnic minorities and farmers whose first child is a girl are excluded from the restriction.

In some areas couples where both parents are only children are also allowed to have a second baby.

Now, Guangdong authorities are seeking permission for some parents who are themselves only children to have more than one child.

"To allow the new policy will have little overall impact on population growth," Guangdong family planning chief Zhang Feng was quoted by the Southern Metropolis Daily as saying.

"The increase in population is still a big problem affecting our social and economic development. But in the long term, ageing will also be a problem."

If approved, the Guangdong trial would help alleviate problems caused by the family planning measure in the world's most populous country, such as an ageing population that is putting pressure on the nation's economy.

The results of the latest nationwide census released in April show 118.06 boys were born in China to every 100 girls over the past 10 years -- an imbalance attributed to the Chinese preference for male heirs and viewed as a possible source of instability.

A study last year warned more than 24 million men of marrying age could find themselves without wives in 2020.

The 10-yearly census also found that more than 13 percent of the population was over the age of 60, up nearly three percentage points from the 2000 count.

He Yafu, an expert who is in close contact with some of China's official demographers, told AFP last year that officials planned to launch similar pilot projects in five provinces to evaluate the effects of relaxed rules.

The proposed test provinces were Heilongjiang, Jilin and Liaoning in the northeast, Jiangsu and Zhejiang in the east.

"Official demographers say that those five provinces have basically been determined as the first pilot provinces, and over the next five years or so it will spread to the whole of China," He said.

The census showed Guangdong was the country's most populous province, with 104 million residents, up from 86 million in 2004.

Much of the population increase in Guangdong, the centre of China's booming export-oriented industry, is due to rapid rises in its migrant labour work force.

Despite the problems caused by population controls, President Hu Jintao said in April the "one-child" policy would continue, because of the increased strain on resources and government services that the population exerts.