A state-run Chinese newspaper on Friday excoriated population authorities for ‘superstition’ after they blamed the inauspicious Year of the Sheep for births falling in 2015 despite a loosening of the one-child policy.

China for decades restricted most couples to a single offspring through often brutally enforced rules and a system of fines for violators.

Authorities long argued that it was a key contributor to China's economic boom, but with the population ageing, the workforce shrinking, and severe gender imbalances it has been loosened in recent years, culminating in a two-child law that took effect earlier this month.

But total births fell by 320,000 last year to 16.55 million, data from the National Bureau of Statistics showed this week.

Many parents say they are reluctant to have more children because of the cost.

A National Health and Family Planning Commission (NHFPC) official attributed the decline partly to it being the Year of the Sheep in the Chinese zodiac. Most of those born in it will be unhappy in life, according to traditional beliefs still held by some.

The official also attributed the reduction to a fall of around five million in the number of women of childbearing age.

Nonetheless, the China Daily, which is published by the officially atheist Communist government, on Friday lashed out at the NHFPC in a rare editorial criticising authorities.

‘The prompt explanation the National Health and Family Commission offered for the reduction in the number of newborns in 2015 sounds farfetched rather than a sincere attempt to recognise the pressing demographic challenges,’ it said in an editorial.

The body's ‘creative use of superstition neither helps understand the real demographic challenges nor adds credibility to the estimate for population growth’, it added.

The issue was ‘crucial to the design of a functioning social security and healthcare system in the long run’, it said.

In 2014 the rules were loosened to allow couples to have a second offspring if one of the parents was an only child, rather than both as previously.

At the time, the People's Daily, the official mouthpiece of the Communist Party, quoted officials predicting the change would add two million births a year in the future.

In the event second child births rose by less than one million that year to 6.06 million, according to the NHFPC, and the rate of increase declined in 2015, when 6.52 million second children came into the world.