The report, compiled by West Bengal Commission for Protection of Child Rights in collaboration with the International Justice Mission (IJM), said the children were subjected to brutal physical violence during conditioning period of the trade which also involved multiple rapes.
The report was released yesterday after on-field study in 2015-16 in the city and neighbourhood areas said.
"Once conditioned, these children were forced to provide sexual 'services' to 7-18 men in a day," the report said.
The overall number of children - both boys and girls - in such places like brothels was no more than 0.8 per cent, the report said.
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Children have been put into the age group of 16-17 years.
In places where sex trade is carried out covertly, like residential premises, massage parlours and lodges, a higher number of 18 per cent children were engaged in such activities, it said.
Of the 131 sex workers sampled in such private establishments, where the information about flesh trade was known only to the select patrons, the number of children engaged in such trade were 24, the report said.
Member Secretary, West Bengal State Legal Services Authority, Ajoy Kumar Gupta said: "One of the worst form of human trafficking is sex trafficking which is most visible in red light areas and a far greater number of them are women and children."
The time has come for more inter-state collabration to fight this menace, Macwan said.
Macwan added, West Bengal has made some of the most progressive anti-trafficking efforts in the country.