More than one hundred thousand people in the southern Pakistan province of Sindh are tied to their employers by "bonded labour" - 12 years after the country's government outlawed the practice.
Jafar was forced to sell his kidney to help pay off his debt
Under bonded labour, landlords - or zamindars - tie their employees to them by debt.
Often the debt is many thousands of rupees - much more than the workers actually borrow. Some workers are taken against their will.
"I was kidnapped with several others," one woman, Shanti, told BBC World Service's Slavery Today programme.
"I was confined alone in a small room. Then the landlord who kidnapped us raped me."
The UN believes 20 million people are enslaved worldwide, with the problem at its worst in South Asia.
Shanti said that she was kidnapped by the same zamindar her family had worked for.
She also said she was two months pregnant when kidnapped.
"The zamindar said when he kidnapped me that if he kept me, then my relatives and other people would come back to his land," she said.
"Then he raped me, saying that because my family wasn't working his land anymore, he had a right to rape me."
Another woman, Laxmi, described similar treatment by her zamindar.
Employers maintain that their workers ask for the loans
"We were severely beaten, and worked very hard by our landlord," she said.
"He had no feeling for human beings. He beat us when we wanted to go somewhere, or even when we asked him for food."
She said the zamindar had told her she owed 100,000 rupees (around $1,700), and her husband the same amount.
"Whenever we asked him for money, he used to beat us in reply," she said.
"We used to think that the entire life of our children would pass, and this debt would still not be paid," she added.
Laxmi has now managed to escape her bondage and lives with a group of other former bonded labourers.
Although they live in poverty, Laxmi said that at least she was free.
"We definitely still feel hunger, but at least here we don't have any torture," she said.
"Previously we were beaten day and night."
Pakistan's government has set up a fund of 100m rupees to rehabilitate workers like Laxmi.
But none of this money has yet been spent. It is estimated five million labourers remain bonded to their employers in Pakistan despite the practice being outlawed.
Ali Aslam of the Pakistan Institute for Labour and Economic Research explained the process by which people end up bonded.
Typically, workers in an industry such as agriculture have to ask for an advance - essentially for subsistence - as their employers will not pay them until after the harvest.
Often bonded labourers work in agriculture, supplying Pakistan's markets
The advance is usually 5,000 rupees ($80-90).
"It's a very small amount, but the next step is additional amounts, so the debt accumulates," Mr Aslam added.
"The third element of debt, which particularly traps agriculture workers, is that they have to share inputs with the landlords - seeds, pesticides and so on.
"So come harvest time, they will have so little left by the time they have redeemed the first cycle of debt, they need to borrow again."
For some people, the debt crisis reaches such an extent they are forced to take drastic measures.
One man, Jafar, told Slavery Today how he had sold one of his kidneys - and other members of his family have done the same - in order to raise money to pay off the debt they owe their employer.
Jafar said he was in "huge debt" and owed around 150,000 rupees. He explained that the debt had increased so rapidly because he had been the victim of duplicity by his landlord.
"We were sometimes drawing 2,000 rupees, and they were writing 5,000 down in the book," he said.
"We are uneducated, we don't know what they have been writing. My parents are old, I wanted to pay off the debts.
"I got 65,000 rupees[for the kidney], almost $1,200."
No free will
Jafar said that selling kidneys was a "usual practice" amongst bonded labourers now and was simply referred to as "donation."
The operation has left him with a 12-inch scar.
"It's nothing really bad, but I can't work now," he said.
"If I do heavy stuff, I start feeling pain."
Jafar said that after selling his kidney his debt was almost paid off - but then his brother had married, and had needed another loan of 30,000 rupees, making the total debt again 70,000 rupees.
"Five people are working and we are getting 200 rupees a day," Jafar said.
"How can we manage the situation?"
However, one employer contended that the system of bonded labour was a benevolent, paternalist system.
Kiln owner Choudhary Muhammad Assan Nazeem said he regarded advances as ways to help his workers make ends meet.
"Almost all of the labourers get advances," he said.
"If the owners does not give them, they will just run away. To keep them working there and to hold them, sometimes it helps us if we have advances against them...
"They ask for advances - we never tie them into advances. They're the ones who ask for money first - and then they have to work."