The scheme to transfer vulnerable child refugees from France to Britain is being ended, the Guardian has learned, leaving hundreds of lone children facing a “daily risk” of exploitation in Dunkirk and Calais.

Charities in France say they have been told by French authorities that only nine more children, who have already been identified, will be transferred to the UK under the Dubs scheme for unaccompanied child refugees.

The Home Office has refused to confirm whether transfers will continue from France, but the Guardian has already heard reports of highly vulnerable children going missing after being told that they stand no chance of getting to the UK legally.

Marie-Charlotte Fabie, director of Safe Passage in France, said the discontinuation of the scheme means there is no way to persuade children to engage with authorities.

This is Alice in Wonderland gobbledygook, they are just playing around with figures Lord Alf Dubs

“I was visiting a children’s centre in northern France last week with UK politicians, and we were told by the people running the centre that they can’t suggest the Dubs route to kids any more, because there will be no more transfers from France to the UK.

“On the same day, we met two Eritrean minors in Calais who said they left the centre when they were told that the Dubs route was closed for now, returning to the streets and camps to try their chance.”

Lord Alf Dubs, after whom the scheme is named, said he intended to challenge the Home Office to keep the routes open from France.

“I will be putting in a question to the government about this on Monday in the Lords. I was in Calais a week ago and it was quite clear there is a desperate need there for safe routes,” said Lord Dubs.

“My understanding is that this is a Home Office decision, that they set sub quotas for France, Greece, so on and are saying the French quota is full.

“This is Alice in Wonderland gobbledygook, they are just playing around with figures. They should take children who are in urgent need, not make it about sub quotas and arithmetic. The Home Office originally set an arbitrary cap of 480 children for this scheme and I challenge this in any case. We know there are local authorities offering to take more children.”

In a filthy camp in Dunkirk, children and families are living in rain-soaked, flimsy tents alongside large groups of men. Children play in rivers of mud while hundreds of teenage boys are at constant risk of sexual exploitation, sharing tents with older men.

Charities say the poor conditions and increasing police violence are pushing children into the hands of abusers and exploiters.

Hayley Willis of the Refugee Youth Service in Dunkirk, a charity that currently has 250 minors on its books, said she sees indications that they are being exploited every day.

“I have a background of working with sexually abused children, so I know the signs. Children who have no money suddenly have an iPhone or new trainers, or they are moved from one camp to another, away from their friends. They self-harm, they turn up drunk, they have suicidal thoughts. We hear: ‘I’m lucky to share a tent with an older guy.’ We hear this daily.

“We had several children who would have been available for the Dubs scheme. They have been in Europe since early 2018.”

A refugee child in the camp at Grande-Synthe, near Dunkirk. Photograph: Stephanie Lecocq/EPA

The only other legal route a child can use to reach the UK is to apply under an EU law known as the Dublin regulation. This allows minors to have their case transferred to another EU country in which they have close family.

Many young people in Dunkirk and Calais are trying to reach family, but it is a very lengthy process. Lawyers say it is now “almost impossible” because of the burden of proof the Home Office requires.

Willis said children often go missing from children’s homes because they don’t believe they will ever reach family in Britain unless they travel illegally.

“Many of our minors – around 20% of our current children – have family in the UK. We want the children to stay in France but they go missing because it takes too long to apply legally. They are not kept up to date with their case, the accommodation is very poor. Sometimes there are not spaces for them.”

In February, said Willis, 54 young people being tracked by the youth service entered the UK illegally.

“When we know they have got to the UK we report them to the NSPCC and the child trafficking advice centre. Four children were recently rescued from exploitative situations after we notified authorities. There is nobody else doing this.”

Staff at the Refugee Youth Service try to build trust with young people so they can track them as the move on.

Salar is 17 and, like most of the refugees in Dunkirk, is from Iraqi Kurdistan. He has family members in the UK with whom he wants to be reunited.

While most of the boys are sleeping in the camp’s appalling conditions, Salar has chosen to claim asylum in France so that he can travel lawfully. Frustrated at the process already, he is considering trying to get on a lorry instead.

“My uncle is in England, my mother’s brother. He has a British passport and has been there 20 years. I talk all the time with him and he tells me [to] wait, do it legally. But I don’t know how long to wait. I have been here two months. If it is one year, I can’t wait that long.”

Salar said his aunt has offered to pay a smuggler. “But they are very worried about me. They are telling me to wait,” he said.

For now, Salar goes back to the children’s home. Other boys sleep in the squalid conditions of the emergency camp in Dunkirk.

‘Exploitation at every level’

Since the Calais refugee camp was destroyed in 2016, police, local authorities and the British and French governments are determined not to allow a permanent camp of any kind to spring up again. The settlement in Dunkirk, emergency winter accommodation provided by the local city council, is due to close in the next few weeks.

Children attend a Safe Passage rally outside Parliament before lobbying MPs on the anniversary of the destruction of the Calais Jungle in October 2017. Photograph: Peter Marshall/Alamy

Maddy Allen, field coordinator for Help Refugees in northern France, said the dire conditions were contributing to young people becoming targets for predators.

“Over winter men would drive up, beep their horn and offer boys food and drinks for sexual favours. Our teams had this reported from the people we support multiple times. This is in a context where the police recently covered food in teargas. This was on 16 April. A week later they cut all their water jerrycans. They have poured bleach into tents. This situation is a recipe for exploitation – it exists at every level. ”

Charities have also collected evidence of water jerrycans being cut by police and chemicals being poured into refugees’ tents.

The Guardian contacted the sous- préfet of Calais with the allegations but they did not respond.

Last week, a number of organisations defending human rights in northern France lost a court challenge over the refusal of local authorities to provide food and water to refugees.

Allen believes there should be basic support for people who arrive in Calais and that the poor conditions are not stopping people coming to northern France.

“You will never, ever stop people crossing. All you will do is make it increasingly dangerous. For a young person who has no money, what are they going to have to do to get across? We know they are being exploited. There is exploitation at every level, for the most basic things.”

The Home Office refused to confirm whether transfers from France are being stopped. In a statement, they said only that the scheme is still open across Europe: “We remain fully committed to relocating 480 children under section 67 and are determined to deliver on that. Over 220 children are already in the UK and transfers of children continue.

“The UK has made a significant contribution to protecting vulnerable children, providing protection to more than 34,600 children since the start of 2010.”

The figure of 480 in total has been set by the Home Office but was challenged by lawyers in the UK high court.

Safe Passage wants the government to make a new commitment to resettle 10,000 vulnerable and unaccompanied children from Europe and conflict zones over the next 10 years, and are collecting pledges from councils who are willing to take children in.

Steve Cowan, leader of Hammersmith and City Council, said after he visited Calais last week that the council would be willing to find places for more children if the government provided financial support.

“We stand by ready to take 200 children, including those we saw last week, who are now missing out on the chance to reach the UK safely. We will do that if the government will provide the funds. Then us and other councils can do what we want to do, and not look the other way.”