Image caption The law in India is vague on when children can legally work

Rescued from forced employment, 13-year-old Lakshmi is frail and frightened.

Two child protection officers hold her on either side as she walks into the police station.

She was abducted four years ago from her village in north-east India.

Until her rescue, she had been working in people's homes across West Delhi - cooking, cleaning and taking care of children.

"I was not allowed to rest," she says. "If I did something wrong or it was not what they wanted, they hit me.

"If I wanted to sit down for a bit because I was so tired, they would scream at me.

"I was never allowed to leave the house, so I didn't realise that I'm in Delhi. My employers told me that we are in Madras in South India."

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As the police and counsellors question her, Lakshmi breaks down. She tells the police that she was sexually assaulted by the men who kidnapped her.

She was threatened that if she told anyone about it, they would tell everyone back home in her village and her honour would be destroyed.

And then, when she started working the agent who arranged her work withheld all her wages leaving her with nothing.

'Lured with clothes and sweets'

Her uncle is just relieved to have found her. A tea garden worker from Assam, he says her parents died when she was young and her grandmother is worried sick about the young girl. He is also angry about the abduction.

"What can we really do? We are poor people - I didn't have enough money to come to Delhi to look for my missing niece.

Image caption Kailash Satyarthi (left) is helping families look for their missing daughters

"Unscrupulous agents and middlemen just come into our homes when parents are away working at the tea gardens and lure young girls with new clothes and sweets. Before they know it, they are on a train to a big city at the mercy of these greedy men."

He is not alone. One child goes missing every eight minutes in India and nearly half of them are never found.

Kidnapped children are often forced into the sex trade. But many here feel that children are increasingly pushed into domestic labour - hidden from public view within the four walls of a home.

The government estimates half a million children are in this position.

Demand from middle classes

At a rehabilitation home in northern Delhi run by a charity for children, Bachpan Bachao Andolan, many families have gathered.

I don't want anyone to go through what I did Sumila Munda

They are all tea workers from the north-east state of Assam and have come here searching for their missing daughters.

They estimate that just from one particular area - Rangpura in Assam - 16 girls have been lost in the last three to four years.

Helping these families find their daughters is Kailash Satyarti, the head of Bachpan Bacchao Andolan.

"This is the most ironical part of India's growth. The middle classes are demanding cheap, docile labour," he says.

"The cheapest and most vulnerable workforce is children - girls in particular. So the demand for cheap labour is contributing to trafficking of children from remote parts of India to big cities."

Media playback is unsupported on your device Media caption This girl was recently rescued after being abducted and forced to work

'Hellish life'

Offering them a ray of hope is the case of 18-year-old Sumila Munda, who was rescued earlier this month. The information she provided led to police arresting a couple of alleged traffickers.

She says she still has nightmares about her employers.

"I don't want anyone to go through what I did. I often wondered if I will ever escape from the hellish life I was stuck in. I had dreams of being in school, studying. Now I will get back to my studies."

Image caption Sumila Munda was recently rescued

India is estimated to have more child labourers than anywhere else in the world.

But while abducting children is illegal, the law is vague on when they can legally work. Child labour law does not allow children under the age of 14 to be employed, but anyone under 18 is legally considered a child.

Government helpless

And the government body in charge of children's rights admits they are helpless.

"Unfortunately our child labour prohibition and regulation act is totally outdated," says Kushal Singh, head of the National Commission for Protection of Child Rights.

Image caption Kushal Singh says the law needs to change

"It says children below the age of 14 cannot be employed in hazardous occupations. Does that mean in non-hazardous occupations a two-year-old child can be employed?

"So obviously it's a very regressive act. This issue has been raised and now an amendment is pending in the parliament. However, it has been pending for a very long time."

If the law changes, it will make the fight against child exploitation a little easier.

But that's no relief for families like these. Many here fear that their daughters may be lost forever.

You can hear more on this story on The World Tonight on BBC Radio Four at 22:00 GMT, or listen again on iPlayer.

*Some names in this report have been changed to protect the identities of victims.