China is ordering local officials to stop using threatening slogans to enforce its strict "one-child" policy, state media has reported.

The government wants to ban slogans like: "Kill all your family members if you don't follow the rule" and "We would rather scrape your womb than allow you to have a second child," the Shanghai Daily said at the weekend.

China, the world's most populous country with more than 1.3 billion people, introduced the "one-child" policy in 1979.

Despite calls for relaxation, Chinese officials say the policy is still needed, claiming over-population threatens the country's development.

But the National Population and Family Planning Commission aims to prevent zealous local authorities from offending the public or worsening social tensions with "nasty" slogans, the newspaper said.

Several referred to forced sterilisation -- one slogan said: "If you don't have your tubes tied, your house will be demolished."

"Once you are captured, your tubes will be tied. Should you escape, we'll hunt you down. If you attempt suicide, we'll offer you either the rope or a bottle of poison," read another.

The newspaper gave no indication of where the slogans were used.

China, under a 1980 policy designed to control its population, permits most couples to have only one child, an approach critics charge is backed with forced sterilizations and abortions.

Some experts say the "one-child" policy has turned into a demographic time bomb as the population ages, storing up huge economic and social problems for the country as well as fostering a gender imbalance.

Given the traditional preference for sons, sex-specific abortions occur and female infanticide and the abandoning of baby girls have also been reported.

New slogans which have received the government's nod of approval include: "Caring for a girl means caring for the future of the nation," the newspaper said, in an effort to encourage families to raise daughters.