China has announced that it will end its controversial one-child policy, according to the state news agency Xinhua.

The Communist party will now allow all couples to have two children, ending a decades long policy estimated to have prevented around 400 million births. It was initially introduced in 1979 to control a huge population increase.

Critics have been urging China to end the policy for years, arguing that it will create a demographic “timebomb” with a soaring ageing population and a rapidly declining work force. The UN estimates that by 2050 China will have nearly 440 million over-60s. The policy has also created a significant gender imbalance, with many parents choosing to abort girls in favour of having a male heir.

China has gradually relaxed the policy over recent years; since 2013 couples in some parts of the country have been allowed to have two children if one parent was an only child. Parents who flout the one child rule risk fines, forced unemployment or abortion and sterilisation.

The announcement was made at the Communist Party’s Central Committee meeting, and was publicised on Twitter. At the meeting, the party is also set to announce growth targets and its next five year plan.