Pedro's life as a sex trafficker began when he offered a sweet to a pretty young domestic servant out on a Sunday stroll in a provincial city in central Mexico. "Once I got her laughing, I knew I was in with a chance," he recalls. "Then I got the sun, the moon and the stars down from the sky for her."

A week later he was roasting a pig at the home of her poverty-stricken family to celebrate their non-existent forthcoming nuptials. Within a month she was working an alley in a northern border city to raise money to help him pay off an imaginary debt. "The merchandise," he says, using the jargon of the Mexican sex-trafficking business, "had been activated."

After many years of largely ignoring the problem, federal deputies approved a people-trafficking law in 2012 that was supposed to spur a nationwide crackdown. So far, however, only Mexico City has responded with any gusto, ratcheting up the number of raids in the name of rescuing victims and arresting traffickers.

"Sexual exploitation is a modern form of slavery," says Juana Camila Bautista, the head of a special prosecutor's office set up last May to focus on the issue. "We are doing battle against this horror."

But the new official concern about sex trafficking in the capital has sparked controversy. Some say the raids have left many important traffickers untouched. Instead the authorities have been rounding up prostitutes and accusing them of complicity.

"If they want to criminalise all sex work they should come out and say it," says Elvira Madrid of the combative NGO Brigada Callejera (Street Brigade), which works with prostitutes in the capital. "Trafficking is one thing, sex work is another."

Another problem is that even well-directed stings in Mexico City rarely dismantle the much broader sex-trafficking networks often generated in other states where the authorities continue to turn a blind eye. It is a problem that some estimate sucks in thousands of women every year.

"At least where I come from, it is seen as a normal job," Pedro says of the collection of towns in the central state of Tlaxcala where he grew up, which are famed for producing pimps the way others produce artisans. Pedro, who was detained in a raid on a hotel in the capital in 2009, adds that the influence of pimps in his home state would almost certainly have protected him from facing justice.

Tlaxcala pimps dominate sexual slavery in the capital, as well as in several other Mexican cities – and the odd US one as well, including New York. And, according to Pedro, there are ever more of them. "When I was a boy, there were a few renowned local families involved," he says. "Now every young man seems to have a brand new car they couldn't have got through any other means."

Pedro became one of them 15 years ago, after a short stint working in a US factory as an illegal immigrant took the shine off the American dream.

To get started, he sought out veterans who had retired and laundered their profits in a string of legal businesses while also keeping their oar in the old trade by initiating younger relatives and eager pupils like Pedro.

Sex workers in Mexico City don skeleton masks during a candlelit vigil for their deceased colleagues, many of whom were murdered. Photograph: Reuters

"They said it wasn't a game and that there would be lots of problems with the police and the girls, and with other pimps who might want to kill me or who I might have to kill. And they asked me if I was conscious of that," he recalls. "I said yes, but the truth was that I was 19 and not conscious of anything other than that I wanted to make money and this was the only option I had."

Pedro's pimping godfathers advised him on how to ensnare poor and lonely Mexican women, often from troubled families. They told him to limit his initial "investment" when going after potential targets to a week, in order to avoid wasting his time.

They also played an active part in his first conquest, the one that started with a sweet. Posing as his uncles, they helped convince the girl's family that Pedro was a hard-working young man with good intentions. Once she was well and truly hooked, they helped him organise a move to the border city of Tijuana, where they ran hotels.

Even so, it was up to Pedro to cajole her into prostitution in the name of paying off a debt, while keeping the dream of a wedding and future happiness alive.

That was in 2000. When he was arrested nine years later, she was still seeing dozens of clients every day, entirely for his profit. By then, Pedro says, he had entrapped about 30 women in similar ways, and usually had six working for him at the same time – each earning $300-$400 a day. "I never had any problem activating my girls," he boasts, before giving a lesson in the language of trafficking that labels women as "furniture" and "merchandise", and talks about new recruits as "fresh meat for the lions".

He never gave his women any of their earnings, though he insists he sometimes took them to dinner or to the cinema and reserved violence for extreme circumstances such as an escape. "I knew lots of pimps who drugged and beat their women all the time," he says. "I knew pimps who kept them near starved and kept their children hostage, but that wasn't the school I was taught in."

This was the nightmare that Veronica lived for years. She met her pimp while working in a brothel just outside Mexico City when she was 15. He approached her as a client, treating her with a kindness she had never known, and promising to take her away to a life of love and security. By the time she discovered that his family owned brothels in the state of Michoacán, where she was expected to work, it was too late.

"They are all the same. They talk to you nicely and they treat you well at first because they see the profit in you," she says. "They look over your face and your body and have sex with you to see if you have potential, and then they start with their rap about how pretty you are and little by little you are pulled in. And when you fall, you are stuck."

A former prostitute wears a piñata as a hat during Christmas celebrations at Casa Xochiquetzal, a shelter for sex workers, in Mexico City. Tlaxcala pimps dominate sexual slavery in the capital. Photograph: Reuters

Things got even worse for Veronica after a failed escape attempt prompted her pimp to move her to the capital, where she was allowed only an hour's sleep a day between seeing about 40 clients.

The pimp's fear that a rival was trying to steal Veronica, or the merest hint of insubordination, prompted vicious beatings. But, Veronica says, what really kept her in line was his family's control of her two children, whom they rarely allowed her to see.

Eventually Veronica did escape, with the help of the activists from Brigada Callejera, who also helped her snatch back her daughter in a daring raid on her pimp's family home. "I tried to save my son but couldn't," she says. "Maybe they will tie him to the business as well. That's the way they do it, the father passing the title to the son."

Veronica laid low for a while until, penniless and with no education, she returned to prostitution, though at least she was keeping her earnings.

A few months ago her trained eye spotted an obvious pimp honing in on her daughter, and the terror came flooding back. "For the first time I told her everything that had happened to me, to make her understand what she was getting herself into," says Veronica, who took her daughter into semi-hiding.

Veronica's pimp was not from Tlaxcala, and nor was the man hitting on her daughter. According to Pedro, this shows that while Tlaxcala pimps may abound, they are not particularly territorial. After all, the supply of vulnerable young women in Mexico can seem close to endless. "This is a free market," he says. "As long as you don't steal another pimp's girls there is no problem."

Pedro insists he is a reformed character with no intention of returning to the business when he is released from jail in a few years, though his expressions of regret appear to be tinged with nostalgia.

"I am sorry I hurt them. Sorry I broke their dreams and illusions," he says at one point. "It was really easy for me," he muses at another, a discreet smile at the memory just visible on his lips.