China will not require prospective parents to obtain approval to have two children under the new "two-child policy", in what appears to be a further relaxation of reproductive controls in the world's most populous country.

A document released by the central government and ruling Communist Party today said families would be able to "independently arrange childbearing" under the new policy, without applying for approval.

The National Health and Family Planning Commission had said in October that couples would still need approval at first.

The document released on Tuesday said implementation of the policy would begin this year, without giving a date.

The two-child policy is itself a relaxation of the "one-child policy" that led to forced abortions and infanticides for decades. Beijing hopes to reduce the pressure of an aging population.

About 90 million families may qualify for the new two-child policy. China, the world's most populous nation, had 1.37 billion people at the end of 2013.