China's top legislative committee is set to formalise landmark reforms to unpopular decades-old policies including abolishing "re-education through labour" camps and increasing exceptions to the one-child limit.

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

The "standing committee" of the country's rubberstamp parliament, the National People's Congress (NPC), is considering the moves during a six-day meeting that began Monday, state-run media said.

"The NPC Standing Committee will vote on the proposal as early as Saturday, which, if passed will mark the end of the half-century old system" of "re-education through labour", the China Daily reported on Tuesday.

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 going to trial -- soon became rife with abuse.

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

"The historical mission of laojiao has been completed," Xinhua said.

Reforms being considered to the one-child policy -- imposed more than three decades ago to prevent overpopulation -- 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.

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

But enforcement of the policy has at times been seen as 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.