BEIJING - Living far from home to earn a living, China's migrant workers can bear tough jobs and shabby accommodation, but it seems they can't ignore their primitive desires.

To relieve the sexual repression caused by long separation from spouses, many migrant workers have "temporary husbands or wives."

The sensitive issue was brought under public debate on Sunday through comments made by a deputy to the National People's Congress (NPC), China's top legislature.

"Some of you may be surprised at such a quasi-conjugal relationship, but it has become more and more common around me and among the whole group of migrant workers," Liu Li, a female deputy from Xiamen in southeastern China, said at a press conference.

Liu, a migrant from central China's Anhui Province, works for a foot massage company.

The temporary couple phenomenon has led to many social problems, said Liu, citing increasing rates of divorce and extramarital affairs in rural areas, and the impact on the next generation.

Back in 2008, "temporary couple" was a fresh phrase and the phenomenon was just "sporadic," according to a non-fiction book written by Wu Zhiping, a writer focusing on rural women.

"The separation of husband and wife has posed a challenge to China's traditional agrarian family pattern, which features men doing farm work in the field and women weaving at home," wrote Wu in "An Investigation on the Life of Rural Women."

But the separation of migrant spouses is sometimes necessary due to high house prices in cities and little access to medical care and educational opportunities for their children.

"Physiological human needs and the failure of traditional binding morality in the original society of acquaintances have both contributed to the increase of temporary couples," said Dang Guoying, a researcher on rural policy with the Chinese Academy of Social Sciences.

When a man or woman comes to a new place, they tend to be more "daring" as few people know them and there is accordingly less of a sense of moral constraint, explained Dang.

Many people keep a tolerant attitude toward casual sexual relations, while others maintain such unions are volatile relationships which can seem okay outwardly but may go awry at any moment.

There are examples of "temporary" couples becoming true couples, building a new family after destroying two.

"I don't think they have better alternatives," wrote "mandy-xiaoai" on the popular microblogging site Weibo. "They just need some emotional support, and it's not rational to judge merely from the perspective of morality."

It rings true to some extent, considering the overall population of migrant workers.

China registered 150 million migrant workers in 2010, 84.9 million of them sexually active men and women born after 1980, accounting for 58.4 percent of the total, according to figures from the National Bureau of Statistics.

But some consider it degenerate. "Don't make excuses for the anomic," "leticia_liu" posted on Weibo.

Li Changping, a rural expert from Hebei University, said one solution to this problem is to accelerate the reform of China's household registration system, which exclude migrant workers from having the same access to public services as urban citizens. The disparity understandably discourages many migrants from bringing their families with them as they search for work.

Migrant workers are not included in health care and other social security systems in their workplaces, and their children can not sit college entrance exams away from where they are registered.

Dang Guoying also urged the government to make more efforts in promoting sound urbanization, bringing down the surging house prices and apply public resources to all urban residents.

At the opening of China's ongoing NPC annual session earlier this month, Premier Wen Jiabao promised to speed up reform of the household registration system and create a fair environment for people to migrate, settle down and work.

"'Temporary couples' will disappear on the premise of an improved quality of urbanization," according to Dang.