Taken by Hazel Thompson (takenebook.com)

A London photographer has revealed horrifying details about India's sex trade and the conditions in which young girls are kept before being pimped on the streets.

Hazel Thompson, who spent 11 years investigating the Indian sex trade, published a book detailing her findings in October this year.

Speaking about her work to delegates at the Trust Women conference in the City of London, she told how young girls were kept in small cages like animals "to break" them before they are put to work as prostitutes, the Evening Standard reports. In another case, she said one girl had not seen daylight for five years.

"Girls are in cages against their will. Would men come to these brothels if they knew they were not paying for sex, they were paying to rape a slave?

"Over the years girls described the box cages to me, saying they couldn't move in the space. This is true. There is evidence. These horrors really exist. Slavery is a reality. For 11 years I have seen the horrors and reality. I heard stories of torture. It is hell on Earth. No one should be left like this.

"This is not a place of pleasure, this is a place of pain"

Unable to escape

Thompson, 35, focused her work in Kamathipura, the red light district of Mumbai where an estimated 20,000 women and girls are forced into prostitution.

Over the last 11 years, she has gained their trust to find out what their lives are like.

One woman, named Guddi, was taken to Kamathipura when she was 11 by traffickers. At the age of 22, she now works as a prostitute and has been unable to escape, despite help from charities.

Speaking at the conference, which was aimed at promoting women's rights, Thompson said awareness must be raised about this problem, explaining many of the women and girls said they would not have been "enticed" by the traffickers had they known where they would end up.

"We need to get eight, nine and ten-year-olds educated before traffickers get to them," she said.

Her ebook, Taken, is available on the iTunes store.