THE ticking time bomb that is the Chinese population has been underlined by a report describing the huge challenges its sheer numbers - 1.3 billion and rising - will present to the country over the next 30 years.

Despite almost three decades of the one-child policy, the population will reach 1.5 billion by 2033, well in advance of previous estimates of 2050, a study by the State Population and Family Planning Commission has found.

The country is already straining from shortages of basic resources such as water and habitable land as the population grows, but the total figure is not the worst of China's problems.

By 2020, the commission's study says, the imbalance between the sexes caused by a preference for boys over girls means there will be 30 million more men of marriageable age than women.

Between now and 2016, the growth in the number of people of working age will increase by 10 million a year, meaning that much of China's remarkable economic growth will be taken up simply with finding them jobs rather than making them richer.

In an extraordinary reversal as the effects of the one-child policy play through the generations, the population will age rapidly, so that by the 2040s the country will have 430 million people over the age of 60, compared with just 143 million now, relying on ever fewer workers to provide them with their livelihood.

The one-child policy introduced in the 1970s was an attempt to counteract the preceding baby boom. But an unforeseen side-effect was that couples would either abort female foetuses or abandon or fail to register girl babies in their desire to ensure the male family line continued.

The figures show that, despite a ban on selective abortions, the discrepancy is getting worse - 118 boys were registered for every 100 girls in 2005, up from 110 in 2000. In the southern provinces of Guangdong and Hainan, the figure had reached 130.

"The increasing difficulties men face finding wives may lead to social instability," the study says, echoing one published internationally in 2004 that traced links between societies heavy with "bare branches", as unmarried men are sometimes known in China, and war.

The growth in the number of working-age people is also an indirect result of the 1960s baby boom, as that generation's grandchildren start to come on to the labour market. Although China's average economic growth of 9 per cent per year over the past 20 years has brought the country to prominence, it is estimated that 7 per cent growth is the bare minimum necessary to soak up the increasing workforce.

The working-age population will peak at an astonishing 1.01 billion in 2016, up from 840 million in 2000, more than that of the entire developed world put together.

There was one silver lining, the study report said: "For a long time to come, China will not be short of manpower."

Telegraph, London