The Government must "act with a lot more urgency" on its promise to bring vulnerable children to the UK from Calais, the charity Unicef has warned.
French President Francois Hollande revealed this week his government is preparing to "completely, definitively" dismantle the Jungle camp near the port town by the end of the year.
In the wake of the announcement, the UK reaffirmed its "crystal clear" commitment to resettle vulnerable children and also ensure those with links to Britain are brought to the country.
But Lily Caprani, Unicef UK's deputy executive director, said this promise needs to translate into urgent action before those children disappear or are pushed into the arms of traffickers.
Speaking to the Press Association of the progress since the Government's pledge earlier this year, she said: "Five, six months later, there are still hundreds of them there. We have seen a few brought over but there are loads that haven't been."
Calling it an "emergency" for the children in Calais, she added: "It is time to keep that promise now and turn into a reality."
Estimating there are up to 1,000 unaccompanied minors in the camp, she described the situation as becoming more "urgent" since the announcement and said there are rumours bulldozers could descend in a "matter of weeks".
"A few months ago they bulldozed half the camp, we know children just scattered, we lost them, they went missing, they were trafficked," Ms Caprani added.
"Our great fear is that is going to happen again - that we will lose these children."
With some vulnerable youngsters waiting "months, and months and months, in the camp", she said children have "given up" on the system because their cases are not being processed or given reassurances they are going to be given accommodation.
"All they know is the authorities are coming to demolish the camp and that it is not going to be a safe place to be," she added.
"We are really frightened for them that they will take matters into their own hands and keep trying to jump onto the backs of trucks and lorries - because they don't feel they have any option.
"The thing that is so outrageous is that hundreds of them have a right to be in the UK. It just seems so wrong that children who have that right are left in complete limbo like this."
She described the camp as "no place for a child", and said it is "frequented" by people smugglers and traffickers, and those who prey on the vulnerability of children.
"They tell us they are frightened," she said, revealing volunteers have reported seeing children as young as eight or nine in the camp.
She said the children in Calais, who have a mistrust of the authorities, need a "solid plan" to reassure them they will be safe and their cases looked at urgently - before the bulldozers pull the Jungle down.
"The Government needs to act with a lot more urgency than it is doing at the moment because the bulldozers are going to arrive and there needs to be a plan for these children as soon as possible," Ms Caprani said.
She added: "Every day that goes past is another day children might be trafficked, or end up being killed."