MUMBAI (Thomson Reuters Foundation) - Fathers in rural India are the target of a new campaign to stop traffickers ensnaring young girls into the sex trade as research on Friday showed the average age of girls forced into prostitution had dropped with some as young as eight.

An 18-month study, led by the My Choices Foundation in partnership with major anti-trafficking groups across India, found the average age of girls being trafficked had fallen to age 10 to 14 in recent years from 14 to 16 in the past.

But a key finding was the role of fathers with researchers discovering traffickers were convincing fathers to give away their daughters by promising to arrange a marriage without the need to pay a dowry to the boy’s family or a job in a city.

Once the girls were gone, however, families rarely found out what had happened to them with no communication at all.

“Girls aged 14, 12, and sometimes even eight have been trafficked,” Vivian Isaac, program director with My Choices Foundation told the Thomson Reuters Foundation, as announcing the launch of “The Good Father Campaign” next year.

“They are taken care of or ‘reared’ until a certain time before being pushed into the sex trade.”

Of an estimated 20 million commercial sex workers in India, 16 million women and girls are victims of sex trafficking, according to non-government organizations working in India.

The study, titled Preventing Sex Trafficking in India, found 90 percent of trafficked girls came from the most marginalized communities and the decision to let a girl leave was usually taken by the father who was often uneducated.

Researchers found 78 percent of girls sold for commercial sexual exploitation were from the eastern state of West Bengal where the state capital is Kolkata.

Official data in 2014 showed that West Bengal accounted for about a fifth of India’s 5,466 cases of human trafficking with the state both a source and a transit location for women and children trafficked into the sex trade.

Reports of human trafficking in India rose 25 percent in 2015 compared to the previous year, with more than 40 percent of cases involving children being bought, sold and exploited as slaves, according to the National Crime Records Bureau.

Isaac said the study would be used to build advocacy programs to highlight the risk of trafficking to fathers in rural India who often had no idea of the dangers.

Researchers found during work in the field that parents were also reluctant to report a missing girl to the police fearing stigma or enmity with a neighbor who brokered the deal.

“They hope for the best. They believe their daughter will find a good job in Mumbai,” said Isaac.