“I sleep here.” 21-year-old Ahmad points to a grubby blanket on a patch of soil beneath an apartment block in northern Paris. It’s 3am in October but the Afghan national wears only a T-shirt. His arm bears a small bullet wound, and a cluster of self-inflicted slashes cover both wrists.

“I got a letter saying if I find you anywhere in Afghanistan, I will shoot you directly like your father,” he says in perfect English, sweeping back an overgrown fringe. “I said to my mother, ‘Goodbye, I hope you have a long life, let’s see if I can make a life.’ But now I’m in Europe, there is nothing.”

Ahmad pulls a folded plastic wallet from his pocket – a document from the French authorities outlining his decision to appeal a rejected asylum claim. “It’s been eight months and I’m still waiting for an answer. I have nobody helping me.”

Refugees in Paris forced to sleep among rats and rotting waste

Several hundred metres from his makeshift dwelling lies so-called “Crack Hill”. Unknown to most Parisians, the strip of conjoining roads at Porte de la Chapelle is infested with rats and rotting waste, and has become a hotspot for drug addicts. Prostitutes pose on street corners as crack addicts shamelessly smoke or inject themselves on the wall. There isn’t a police officer in sight.

Charities warn that the proximity of this lawless hub to scores of sleeping refugees – of which there are an estimated 800 on any given night – is a “recipe for exploitation”, as vulnerable asylum-seekers with no right to work are lured into transporting drugs and even selling their bodies in order to earn money to survive.

Yards away, on a concrete island between two main roads, a large cluster of blankets and sleeping bags marks the sleeping bodies of several dozen West African men, some just boys, bedding down for the night. Others sleep in a narrow ditch running alongside the road, among the rats and abandoned litter.

“Trying to find somewhere to sleep which isn’t dangerous is impossible for a lot of refugees – and it makes them perfect prey for exploitation,” says Heather Young, a veteran volunteer who has embarked on night-time distributions in the area for the last four winters.

Being on the streets makes refugees vulnerable to exploitation (Heather Young)

“There is this really young boy from Somalia. We knew him seven weeks ago. He still had a fresh face. Now he is cracked out. In seven weeks he’s just plummeted. He’s a slave to all of it.”

Heather, who tours the area every other night with Paris Refugee Ground Support, makes reference to Ahmed, saying she found him a few nights ago with “sore and bloody forearms” after he spent his birthday alone.

He comes from a wealthy family and was well-educated in Afghanistan, but now, with just a blanket and a crumpled asylum claim, he has no choice but to rely on “black work” to live.

“The kid needs help, but the only way for him to survive is to find work – black work. He tells me he’s working six-hour shifts for 20 euros for some ‘food chain’. It’s a recipe for exploitation,” Heather says.

The risks facing refugees in Paris are exacerbated by increasing delays on the French authorities processing asylum claims, and a lack of support or legal means of earning money in the interim period, making homeless refugees malleable prey.

Rats and rotting waste where refugees are forced to sleep (May Bulman)

Unaccompanied minors, of which there are up to 100 out each night, are eligible to state support under child protection law, but many are initially refused – with 50 per cent overturned on appeal. Appeals take between two to 14 months, with no support offered during this time.

“They are left without anything, so they become invisible, and then it’s just violence and exploitation,” says Alix Geoffrey, head of Utopia, a charity supporting homeless child refugees in Paris. “People with bad intentions who stumble on to a kid who is isolated and on the street and see an opportunity to abuse.”

Alix explains that sometimes drug dealers will tactically offer hard drugs to young refugees for no cost, promoting it as a form of escape, so that they develop addictions and become dependent.

“They’re very aware of how to do it. They offer it for free the first time and the second time, and then say okay you can have it if you go sell this for me, and it’s very quickly too late,” she says.

“We’ve had a few cases where we see the kid and recognise them from six months or a year before, but they are evidently hooked on drugs. It’s too late to do anything. We don’t have the skills to intervene.

There are reports of refugees being offered shelter in return for sexual favours (May Bulman)

“We’ve known of girls being raped. There was one 16-year-old girl recently who we took to the police because we were concerned about her. But she ended up back on the steer, and experienced a rape attempt.”

Volunteers say teenagers with no option but to sleep on the streets are also vulnerable to sexual grooming and exploitation, with adults allegedly offering them shelter in return for sexual favours.

“A lot of minors will come to us and say they have been staying somewhere, but they know what this person wants in return,” says Alix. “They’re staying with women and men who are exploiting them.

“But when you ask them for more information they completely close up. That’s why it’s very difficult to know how often this is happening and to report it to the police.”

Beneath a large underpass close to the drugs area, another Afghan male, who doesn’t look older than 17, with wide eyes and clear skin, is walking alone and in tears following a scuffle with some men over a sleeping bag.

Drug dealers tactically prey on the young refugees (May Bulman)

“He will be perfect prey for so many people here,” says Heather, after comforting the boy and bidding him farewell. “The tragic thing is, we can’t help him. There are so many like him, and we have no power to help.”

At around 5am, as the darkness fades into the approaching dawn, the toxic buzz of Crack Hill begins to die down. Refugees lie still under their donated blankets and sleeping bags, and Ahmad is tucked alone on his patch of soil. For a moment it feels peaceful.

But within hours, police will arrive to clear them away. The refugees will blend into the city for another day until they are forced to become part of Paris’s criminal underworld once again.

The French police have been approached for comment.