In December 2005, photographer Peter Pattisson travelled to India to photograph the realities of bonded labour. Even though he was familiar with the issues, he was shocked by what he found.

We almost ran Gurbachan Singh over. Driving through the thick fog of a winter's night in the northern Indian state Punjab, our driver could barely see the road, let alone the man standing by the side of it. After all, you don't expect people to be out in the fields working late at night. But for Gurbachan Singh, and many of the estimated millions of bonded labourers in India, it's all in a day's (and night's) work.

As a bonded labourer, Gurbachan is a 24-hour slave, on call for his landlord at any time. Having lived in India for four years I had come to expect the unexpected, but nothing could have prepared me for the month I spent in the Punjab photographing the lives of bonded labourers.

Sigren's story is just one of many that I heard which illustrate the curse of debt bondage. At the age of 12, Sigren was sold into slavery for 1,563 rupees (US$35). A broker travelled with him from his home state in east India to hand him over to a landlord in the Punjab. Promised an annual salary of more than 15,630 rupees, Sigren worked for almost four years before his landlord agreed to pay him anything. "I was not allowed to call home. My owner snatched the phone number," Sigren told me. "When I complained about not getting paid, he called the police to beat me up."

Sigren was freed thanks to the work of one of Anti-Slavery International's partners, Volunteers for Social Justice (VSJ), an Indian NGO led by Jai Singh. Jai fights slavery using the same tool that anti-slavery campaigners used 200 years ago: the law. Under Indian law, "the bonded labour system shall stand abolished and every bonded labourer shall … stand freed and discharged from any obligation to render any bonded labour," the Bonded Labour (Abolition) Act says. "If we followed the letter of the Act," Jai explained, "most landlords would be in jail, even animals have more rights than bonded labourers. The law states that animals must not work for more than eight hours a day, but bonded labourers work all day, every day. Bonded labour is a trap, not an alternative to no livelihood at all."

Ram Singh is one of the many bonded labours VSJ has helped. Ram managed to escape from the landlord for whom he worked without pay, for 12 years. His landlord, however, simply kidnapped his son to work in his place. Early one morning, armed with a writ from the Punjab High Court, we set out on a raid to free his son, Kamikar Singh. Five hours later, in a remote field we found Kamikar spraying pesticides on his landlord's crops. Faced by a court official, a phalanx of police and a foreign photographer the landlord quickly set Kamikar free.

However, vested interests and the caste system conspire against Jai Singh and his fellow activists. Landlords, local administrators and the police all come from the same caste, making it harder to pursue prosecutions. Jai tells the story of one court official he caught accepting a huge bribe from the local police chief hidden in a box of sweets.

The caste system allows landlords to act with impunity. One afternoon we received a phone call from a village in southern Punjab. The landlords of the village had accosted and abused four bonded labourers for refusing to work or pay back their loans. There were rumours that their homes had been burnt down. To speak to the landlords in the village I convinced a local journalist to introduce me.

Jasmer Singh, one of the landlords involved, was unrepentant. "We take loans and pay them back, why can't our workers?", he asked. I asked him about his relationship with his labourers. "It's a father-son relationship," he replied, "they are like my children. Whatever they want, I'll give them." On the other side of the village I heard a different story. Gurmail Singh, one of the bonded labourers accosted by Jasmer, had fled the village in fear. His father explained that Gurmail had received an advance of 27,360 rupees but after 10 years of work he had received no salary and was still working off the interest on the original loan.

Even when Jai and his staff do manage to free a slave, I discovered that landlords have their own means of exacting revenge. Meetu Singh and 16 other members of his village filed court cases to free themselves from bondage. In response, the local landlords imposed a social boycott against them and their families. The boycott meant no one would offer them alternative work, shops would not sell them goods, doctors would not distribute medicine, their cattle could not drink at the village pond and their children were barred from the local school.

Fearing retribution from the landlords, other lower caste families refused to unite against the boycott. "We have no power because we have no unity," explained Meetu. But when I asked him whether he had any regrets about filing the case against his landlord, there was no hesitation in his reply, "we would hang ourselves before going back into bondage."

Africa Programme Officer Romana Cacchioli visited Niger in January and returned with stories of hope from recently escaped slaves and news of progress in the fight against descent-based slavery.

About 40 kilometres from Abalak in central Niger, we finally found her encampment. Sitting surrounded by her four children, Assibit smiles and laughs. She tells me that her life has changed more than she could ever have imagined. Born into slavery, she worked for her master's family from a young age, but after her master forced her to stand all night serving as a tent post throughout a violent storm, she could finally take no more.

"Life is still hard, you can see we have very little - just this tent, a few pots and blankets, but I am free, I am happy, my children are free and they are happy. In the evenings we eat together, we sit and talk about the future, about how very soon my children will marry. Now we have a future." These seemingly normal aspects of family life are unimaginable for a slave. "No one beats or insults us any more. I can begin to be a mother, and my children are safe," she continued.

Assibit survives with help from our partner Timidria; "I have never known such kindness. They helped me buy seeds, and now I have a small plot near the water pool where I grow beans, pumpkin and greens, and my sons are able to find paid work. Soon we hope to buy some goats and perhaps a donkey."

Assibit's recovery brings hope, and she is not alone. On the way back to Niamey, we stopped at a small village in the desert. There, I met a group of women who had been sold by their masters. One, Marianna, was eager to tell me about her life and her recent transformation. "I was sold when I was a child, and then worked for my master, all day everyday. He beat me and his wife beat me. One day while I was in the market, I heard someone from Timidria talking about slavery, about how it was wrong and that masters could be sent to jail.

"I immediately ran back to the village, grabbed my children and together we came back to town. I found the people from Timidria and they helped me begin my life anew."

When Marianna's master came looking for her, the villagers told him they would contact Timidria if he persisted. "He went away and has never come back," she said. "Now I live in peace. I knew something was wrong with my life, but I didn't know what to do. Today, I am treated as an equal in this village. Now I have friends and I hope to find a husband."

The decision to leave slavery is not an easy one. Slaves face violence from their masters and a world that is completely unfamiliar. But news that slavery is illegal and that Timidria can help is spreading.

My latest visit to Niger shows that things are changing. It is just over 12 months since the Government denied the existence of slavery and arrested Timidria's president, Ilguilas Weila. Weila was released last June, and he is confident that the charges against him will soon be dropped. Our meeting with the Prime Minister's office was also positive. I left Niger feeling that we had turned a corner and hopeful that co-operation with the Government in fighting slavery can begin again.