Image caption Chris Rogers encounters many young girls on the streets of Brazil

Young children are supplying an increasing demand from foreign tourists who travel to Brazil for sex holidays, according to a BBC investigation. Chris Rogers reports on how the country is overtaking Thailand as a destination for sex tourism and on attempts to curb the problem.

Her small bikini exposes her tiny frame. She looks no older than 13 - one of dozens of girls parading the street looking for clients in the blazing mid-afternoon sun. Most come from the surrounding favelas - or slums.

As I park my car, the young girl dances provocatively to catch my attention.

"Hello my name is Clemie - you want a programme?" she asks, programme being the code word they use for an hour of sex. Clemie asks for less than $5 (£3) for her services. An older woman standing nearby steps in and introduces herself as Clemie's mother.

I usually have more than 10 clients per night - they pay 10 reais each - enough for a rock of crack Pia, 13-year-old prostitute

"You have the choice of another two girls, they are the same age as my daughter, the same price," she explains. "I can take you to a local motel where a room can be rented by the hour."

I make my excuses and head towards the bars and brothels of the nearby red-light district.

Despite assurances of a police crackdown, there appears to be little evidence of child prostitution disappearing from the streets of Recife. In four years' time, the country will be hosting the World Cup, which will fuel its booming economy.

Brazil has defied the global economic downturn thanks, in part, to its exotic, endless beaches attracting record numbers of tourists.

The country's erotic reputation has long been attracting an unwanted type of tourist. Every week specialist holiday operators bring in thousands of European singles on charted flights looking for cheap sex. Now Brazil is overtaking Thailand as the world's most popular sex-tourist destination.

Underage

As night falls, the sex tourist's playground in Recife, in the state of Pernambuco, comes alive. Prostitutes mingle with tourists, dancing at their sides and eyeing up potential business. The legal age for prostitution is 18, but many look much younger.

Image caption Two young transvestites say they need to work to get money for food

Taxi drivers work with the girls who are too young to get into the bars. One offers me two for the price of one and a lift to a local motel.

"They are underage, so much cheaper than the older ones," he explains as he introduces me to Sara and Maria.

Neither has made any attempt to disguise their age. One clings to a bright pink Barbie bag, and they hold each other's hands looking terrified at the possibility of potential custom.

Recife's red-light area is now crammed with cars slowly crawling past groups of girls parading their bodies.

One of them, Pia, is dressed in a cropped pink top and mini skirt. The 13-year-old agrees to speak to me about her life as a child prostitute. She explains that she works from the same street corner every night until dawn to fund her and her mother's crack cocaine habit.

"I usually have more than 10 clients per night," she boasts. "They pay 10 reais (£3.50, $5.50)) each - enough for a rock of crack."

Entire streets are now cleared of prostitution - my aim is to intensify these raids in time for the World Cup Eline Marques, Secretary of state for child protection, Fortaleza

For safety, Pia works with a group of older girls who act as pimps, taking care of the money and watching over the younger ones.

"There's lots of girls working around here. I'm not the youngest, my sister is 12, and there's an 11-year-old." But Pia is worried about her sister: "Bianca hasn't been seen for two days since she left with a foreign guy," she says.

Pia first started working as a prostitute at the age of seven, and Unicef estimates there are 250,000 child prostitutes like her in Brazil.

"I've been doing it for so long now, I don't even think about the dangers," Pia tells me. "Foreign guys just show up here. I've been with lots of them. They just show up like you."

Crackdown

Just a couple of streets away the pavement is lined with transvestites touting for clients. Among them 14-year-old Ronison and 12-year-old Ivan.

The cousins look convincing in their stilettos, mini skirts and blouses, and heavy make up.

"We need to earn money to buy rice and staple foods for our families," Ronison explains as he flicks back his long bobbed hair. "Our parents don't worry about us too much. We tell them when we are leaving and when we're coming back. And then we give the money to them to buy food. They know how we get the money, we just don't discuss it"

Image caption The city of Fortaleza has been carrying out relentless clean-up operations

Most sex tourists used to head to the city of Fortaleza some 500 miles away.

But not anymore. For the past year, the state capital of Ceara - which also a World Cup host city - has been sending a clear message to sex tourists that they are not welcome. Every week a dozen armed cars and federal police armed with AK-47s sweep through the streets of the red-light district, breaking down the doors of motels and brothels, arresting offenders and taking underage girls into care.

Eline Marques, the city's secretary of state for child protection, claims her relentless raids are having an effect.

"We have shut down many establishments in Fortaleza. Entire streets are now cleared of prostitution. My aim is to intensify these raids in time for the World Cup, targeting the very tourism that encourages child prostitution," she says.

Other states have indicated that they are monitoring Ms Marques' campaign and, if deemed successful, could follow suit.

'Terrified'

But for every sex establishment that is shut down, every sex tourist arrested, there are victims.

Many are taken to charity run homes. The Centro de Recuperacao Rosa De Saron near Recifi is full to capacity because many of the girls can't be returned home to the poverty that drove them into prostitution. They are sent there from all over Brazil.

Image caption Love Motels can be hired by the hour

Twelve-year-old Maria wants to live with her mother but she can't because her pimp, who forced her to work on the streets and in brothels, threatened to kill her if she tried to escape. She told me that she is still terrified for her life.

"I had no choice but to do what he said. I felt I was losing my childhood, I was only nine years old," she says. "I was scared. Sometimes if I came back without money for him he'd hit me."

Jane Sueli Silva, who founded the centre, says most of the girls are between 12 and 14 when they arrive.

"Many of them arrive here with serious problems like cervical cancer," she says. "As the cancer is normally at only early stage, we can help them and thank God the cure is normally always successful."

Some girls also turn up pregnant, their child fathered by a sex tourist.

Hopes

The British charity Happy Child International plans to build more centres to house a growing number of child prostitutes.

"The crisis for these children turning to prostitution has increased significantly in the north-east of Brazil over the last few years, fuelled by increasing numbers of foreign tourists who travel to Brazil for sex holidays," says Sarah de Carvalho of Happy Child International.

"It is so important to take the children away from the lure of the streets and break the cycle and give them a safe place to live and receive help."

But charities and police crackdowns have yet to reach children like Pia, the 13-year-old prostitute whom I met on the streets of Recife.

Every day I ask God to take me out of this life Pia, 13-year-old prostitute

Her home is a small shack she shares with her mother, two brothers and 12-year-old sister, who had still failed to return home. It was nothing more than a crumbling shed with two sofas acting as a bed and a plastic bucket to wash clothes and plates.

When I asked Casa if her daughters' work in prostitution breaks her heart, she appeared more concerned that they fail to bring home money. "If they make money they don't bring it home. No - they don't bring any money home," she said.

Pia told me that one day she hopes to break out of prostitution. She said she had heard of charities that provide a home for girls like her.

"Every day I ask God to take me out of this life. Sometimes I do stop, but then I go back to the streets looking for men. The drug is bad, the drug is my weakness and the clients are always there willing to pay."

Our World: Brazil's Child Prostitutes is broadcast on BBC World and the BBC News Channel on 31 July and 1 August at various times