Image copyright AP Image caption China has one of the biggest gender imbalances in the world due to the one-child policy and traditional preferences for male children

A Chinese professor's controversial suggestion that poorer men could share wives has sparked debate online on how to solve China's gender imbalance.

Zhejiang University economics professor Xie Zuoshi's proposal has been met with heavy criticism that it is immoral.

China has one of the biggest gender imbalances in the world, with about 118 boys born to every 100 girls.

The imbalance is largely due to the one-child policy and cultural preferences for male children.

Increasing wealth and population movement also means many women are leaving the countryside to work in cities, with men who stay behind struggling to find partners.

'Value of women'

In a piece that was widely picked up by local media, Prof Xie noted there were reports that China could possibly have 30 to 40 million bachelors by 2020.

The huge demand for women and the lack of supply would result in the "value of women going up", he wrote.

"Men with high incomes will have an advantage in finding women, because they can afford the high price.

"And what about the low income men? One way is for several men to band together to find a wife. This isn't some pie-in-the-sky idea of mine. In some remote and poor areas there are cases where brothers jointly marry one wife, and they can live happily and harmoniously."

Image copyright AFP Image caption More Chinese bachelors have taken to marrying women from neighbouring countries, including this Vietnamese woman

He also advocated for greater economic growth so that poorer bachelors could earn more income and could thus attract women from other regions such as South East Asia or Africa.

The shortage of wives in some rural parts of China has led to more men marrying women from neighbouring countries such as Vietnam and Myanmar, but has also fuelled human trafficking. and wedding scams.

'Serious social problem'

Prof Xie's essay, which was published last week and later picked up by Chinese media, attracted mostly appalled derision from readers, who criticised his idea as immoral and illegal.

"If you can't find a mate then don't bother, if women are just only meant for producing heirs and have to mate with many men just to solve the population growth issue, how does this make us any different from animals?" said Weibo user Superelfjunior.

Jing Xiong, a project manager with Chinese women's rights group Media Monitor for Women Network, told the BBC that the gender imbalance problem "is basically a problem stemming from teachings that prioritise men over women".

"And now the solutions are still very much male-centred. This is extremely ridiculous."

"Prof Xie's suggestion ignores the wishes and rights of women, and casts women as tools used to satisfy men's needs for sex, marriage and reproduction... this suggestion is basically sexual discrimination."

Image copyright Sina Image caption Prof Xie's blog essay was entitled "30 million bachelors is a groundless fear"

In a subsequent essay, Prof Xie said he had been bombarded with angry phone calls and comments on social media.

But he stuck to his guns, arguing that laws and morals were mutable.

"If we wave the big stick of morality, keep to the one-husband-one-wife social contract, and let 30 million bachelors have no women and no hope, they hate society, then we would have a serious social problem."

"So please don't talk to me about morals. If we don't let the 30 million bachelors have women, their lives would have no hope and then they may go around raping, killing, setting off bombs... (let me emphasise that this is a possibility, I'm not saying they would definitely do that). Don't tell me that is your morality?" he said.