More than 10,000 peole are now living in the Calais "Jungle" and one in ten of these is a child on their own.
Latest figures from Help Refugees show 10,188 people now live in the camp, which is under imminent threat of being demolished.
Of these people, 1,179 are underage and 1,022 are unaccompanied, a 51 per cent month-on-month increase in unaccompanied minors since August when there were 676.
Sudanese refugees are the most numerous, making up 43 per cent. A third are from Afghanistan. Syrians and Iraqis represent one per cent each.
The refugees are waiting for as long as eight months to be offered even temporary shelter by local authorities as the population rises.
Help Refugees said: "Conditions around the camp are becoming more perilous, with increased and increasingly heavy-handed police presence, the continued hardening of public attitudes towards the refugees, and the continuous threat from local authorities that the camp will be destroyed completely without any alternative means of accommodation being provided.
Help Refugees also condemned the UK's resettlement system as "inert", even for children with a legal right to enter Britain. One of these, an Afghan boy aged 14, died on Friday as he was trying to jump onto a moving lorry on the road between the camp and the port. He was the third child to die this year.
Annie Gavrilescu, Help Refugees' field manager in Calais who carried out the census, said: "1,179 children now live in the Jungle. Only 94 are with their parents and a further 63 live with extended family. 1,022 are alone. In the early hours of September 16, one of these children, a young 14-year-old boy, was run over by a car and killed. The driver did not stop.
"He had been waiting to be legally reunited with his family in the UK, but lost hope and tried to jump on a moving lorry. He fell and was hit by a car.
"With an impending eviction there is currently no plan for safe accommodation for the children remaining in the camp. Those still stuck in the Calais 'Jungle' report increasing instances of self-harm, police violence, deteriorating mental health, insufficient food, inadequate accommodation and feeling hopeless."
Referring to the amendment introduced into parliament by Lord Dubs allowing unaccompanied minors to be allowed in to the UK, she said that so far not a single child had been admitted under this provision.
"All these kids want is to reach their families and somebody in an office wearing a suit is preventing them from doing that by refusing to sign a bit of paper. All this time the Home Office and the French authorities are blaming each other and using children as pawns – it's disgusting politics."
