The effort to gather a body of evidence against the powerful people behind trafficking launches next week in West Bengal, the hotspot of the illegal trade in people, with more reported cases than any other state.
Campaigners say while girls may be rescued and brothel owners arrested, traffickers usually evade prosecution.
"Investigations need evidence to connect the dots on how the trafficker took a girl from a village and sold her to a city brothel," said Pompi Banerjee, programme manager at Sanjog charity that works with trafficking survivors and is supporting the study.
"But in most cases, brothel managers say they never bought the girl and that she came on her own. So there is no mention of the trafficker. We want to build this evidence against traffickers and share it with the government," Ms Banerjee told the Thomson Reuters Foundation.
Starting next week, nine NGOs working with sex trafficking survivors in two major trafficking hubs of West Bengal - the districts of North 24 Parganas and South 24 Parganas - will ask survivors about their journey from villages to brothels.
The survivors will be asked to detail the appearance of their traffickers, their addresses if known and if the traffickers were ever arrested.
The survivors will also be asked and if they are aware of the same person involved in trafficking of more girls.
"This is the first time we are mapping traffickers like this. We have anecdotal evidence against traffickers who continue to procure and sell girls even after a girl they sold was rescued and is back home," Ms Banerjee said.
Recent government crime data shows there were 8,132 human trafficking cases last year against 6,877 in 2015, with the highest number of cases reported in West Bengal, followed by Rajasthan.
South Asia, with India at its centre, is one of the fastest-growing regions for human trafficking in the world.
Of an estimated 20 million commercial sex workers in India, 16 million women and girls are victims of sex trafficking, according to non-government organisations.
While nearly 11,000 people were arrested for human trafficking last year, about 160 people were convicted, government data shows.
Studies show that traffickers have come up with ingenious ways to cover their tracks.
Campaigners say many survivors live in fear as traffickers can intimidate them, forcing them to withdraw cases, flee their homes or drop out of school.
"We had over 100 cases in the last two years from survivors threatened by their traffickers as they were pursuing cases against them," said Subhasree Raptan, coordinator of a non-profit that rehabilitates survivors.
"We have evidence against many traffickers, but this collated data will show how traffickers enjoy impunity and will be an eye opener for the authorities."