Often brutally enforced with abortions and sterilisations, the rules have had complex and enduring repercussions.

Li's parents already had one daughter -- born with the right paperwork -- and were on long-term disability leave from their jobs as factory workers when her mother accidentally fell pregnant. They did not want a second baby, she said, but she was too ill to terminate the foetus.

Families who violate the rules must pay a "social maintenance fee" to legalise their children and secure them a "hukou", Communist China's all-important household registration, which ties crucial government services to one’s official place of residence.

Authorities set Li's at 5,000 yuan -- far beyond the 100 yuan a month in benefits that her parents lived off, even before her mother was formally dismissed once her factory learned the news.

Now 22, Li has always existed in an administrative netherworld.

She realised she was unlike other children at the age of six, when neighbourhood playmates were sent off to school and warned off her company by their parents.

"I began to see that my life was entirely different from those around me, and it was because I had no hukou," she told AFP.

Her mother Bai Xiuling added: "She used to cry and tell me, 'Mom, I just want to go to school!', but there was no way for her to do so.

"We’d have to go to the neighbours to beg for some medicine if she was sick."
- Tiananmen Square -
official population stood at 1.37 billion at the end of last year, and 2010 census data showed that the country has 13 million "black children" like Li -- more than the entire population of Portugal.

Li’s sister Li Bin, eight years older, eventually taught her to read and write. But while children her age were off at lessons, Li was shuttled out every day to stand outside government buildings, where her parents hoped someone would hear their pleas.

"We went countless times. Pretty much every day, weather permitting, sometimes twice a day," said Bai, 59.
In the symbolic heart of the Chinese state, Tiananmen Square, Li held up a sign reading "I want to go to school."

"No matter where we went we were ignored," she said, with lawsuits similarly in vain.

But their efforts did not go unnoticed. The family say  they have endured a decade of police surveillance, including several beatings for the parents -- one of which left them bedridden for two months.

When Li’s father died last November, plainclothes police stood outside the hospital door.

"Her dad would always tell her to never give up hope. He passed away with his eyes open," Bai said in tears. "How can he rest in peace? Of course he can’t."

Implementation of the family planning policy has always varied across China, and a few areas have said they will start granting hukou to people whose parents have not paid the fines.

Contacted Sunday by AFP, a man at the Li family's local police station said: "If she comes to us, we will handle her hukou for her."

But Li said: "In the past 22 years, I’ve seen all too well how the government will say there’s this or that legislation or reform, but nothing actually changes on the ground."

Her mother added: "We’re weak, and they’re strong."
- 'She's lost so much' –
The family live in two rooms of a shared house in Beijing, with no bathroom.

Li Bin dropped out of school aged 16 to support the family, getting jobs at KFC and later at an electronics company.
The pressures have seen her own marriage dissolve, but she bears her sister no resentment, saying that for "standard, legal work", employers could never take on someone without an identity card.

"We all really dote on Li Xue, because we just feel that she's already lost so much,” she said. "We want her to feel warmth within our home, because there’s no way for her to feel warmth out in society."

For now, Li Xue has found work at a restaurant willing to look past her undocumented status.

"For the first time, I’ve been able to be judged on the basis of what I can do -- my skills, not my status -- and it feels great," she said.

But she added: "This job is temporary. My future, I can’t even imagine it."She was born in Beijing and has lived there all her life. But like millions of others conceived in violation of China's one-child policy, as far as the state is concerned Li Xue does not exist.

She has no right to schooling, health care or a formal job. Without a birth certificate or identity papers, she is a "black child", an alien in her own country -- unable to join a public library, get legally married or even take a train.

"I was born here, but I don’t have any of the rights of a Chinese person," she said. "Whatever I do, I’m blocked and have difficulties. There is nothing in China that proves whether I even exist or not."

Last week Chinese authorities announced the end of the hugely controversial policy, which restricted most couples to a single offspring. Instead all families will be allowed two children.