China's top legislative committee voted Tuesday to abolish "re-education through labour" camps introduced more than half a century ago, saying they had served their purpose.

The standing committee of the rubber-stamp parliament, the National People's Congress, also supported the easing of another unpopular decades-old policy -- the one-child limit.

The ruling Communist Party had announced the long-sought changes among a series of pledges after a key gathering in November.

"Lawmakers acknowledged the important role laojiao (re-education through labour) had played in safeguarding public security, maintaining social stability and correcting offenders," the state news agency Xinhua reported.

But they agreed that the programme has been superseded by other correctional schemes, new laws and amendments, it added.

The decision came during a six-day meeting that began Monday.

China introduced re-education through labour in 1957 as a speedy way to handle petty offenders. But the system -- which allows a police panel to issue sentences of up to four years without trial -- soon became rife with abuse.

The camps have become "superfluous" as the country's legal system has developed, Xinhua said late Monday, citing a bill put forward by the State Council, or cabinet.

"The historical mission of laojiao has been completed," it added.

Legislators also backed an easing of the one-child policy, which was imposed more than three decades ago to prevent overpopulation. This would allow couples where either parent has no siblings to have two children.

The exception is meant to counter China's looming demographic problems, including a swelling elderly population, shrinking labour force and gender imbalance.

China's sex ratio has risen to 115 boys for every 100 girls, while the working population began to drop last year, Xinhua said.

The birth rate has fallen to about 1.5 since the 1990s, well below the replacement rate, it added.

"While upholding family planning as an essential state strategy, lawmakers agreed with the State Council that the policy should be adjusted in the face of a steadily declining birth rate and changing demographics," the news agency reported Tuesday.

China argues the one-child limit kept population growth in check and eased the country's rapid economic development.

But its enforcement has at times been excessive.

One such case caused a public outcry last year, when photos circulated online of a woman forced to abort her baby seven months into her pregnancy.