Shanghai is to urge eligible couples to have two children, as worries about the looming liability of an ageing population outweigh concerns about over-stretched resources.

The Shanghai policy, reported by the China Daily, marks the first time in decades that Chinese officials have actively encouraged more procreation.

China's famous "one child" policy is actually less rigorous than its name suggests, and allows urban parents to have two offspring if they are both only children. Rural couples are allowed a second child if their first is a girl.

But since the late 1970s worries about developing an already highly populated country without straining scarce land, water and energy supplies has meant the government has always pushed to keep families as small as possible.

This is still the official line in most of China, but Shanghai is now apparently rich enough to focus on a new concern - the burden of an ageing population on the generation born since the one child policy was unveiled.

The US-based Centre for Strategic and International Studies warned in April that by 2050 China will have more than 438 million people older than 60, with more than 100 million of them 80 and above.

The country will have just 1.6 working-age adults to support every person aged 60 and above, compared with 7.7 in 1975.

"We advocate eligible couples to have two kids because it can help reduce the proportion of ageing people and alleviate a workforce shortage in the future," the China Daily quoted Xie Lingli, head of the city's Family Planning Commission, as saying.

Volunteers and family planning officials will make home visits and distribute leaflets to promote slightly larger families, and even provide emotional and financial counselling.

Shanghai's over-60 population is already move than 3 million, or more than one-fifth of residents. But that proportion is expected to rise to around one-third by 2020, as the children of a baby boom promoted by former Chairman Mao Zedong age, the paper said.

China is ill-prepared to cope with its greying population, with an underfunded state pensions system and shrinking family sizes removing a traditional layer of support for elders.

But if Beijing changes tack on policy, it may not be difficult to shift the population balance.

More than two-thirds of women would like to have two or more children to prevent their children becoming spoilt or lonely, a senior official at the National Family Planning Commission said earlier this year.

- Reuters