The population of the "jungle" migrant camp in Calais has swelled to a record level of more than 7000, the latest survey shows. 

As authorities in Calais threaten new evictions, and step up the pressure to move the camp across the Channel in the wake of the Brexit vote, charities working with the migrants predicted numbers could be as high as 10,000 by Christmas.

Numbers trying to reach Britain from France have increasing daily, in spite of a belief that Ramadan would reduce the stream of migrants. The population has reached a record 7,037, well above numbers seen before the eviction last  February. Of these, 761 are minors including 608 unaccompanied children, the youngest of whom is just eight years old. The youngest child in the camp is aged four months.

The new census from Help Refugees and L'Auberge des Migrants represents a of 15 per cent month-on-month.

The increased border security between Turkey and the EU failed to cut numbers.

Attempts by France and Britain to discourage people from making the journey have also had little effect. Mayor of Calais Natacha Bouchart recently threaten a fresh eviction "as soon as possible".

If the current arrivals rate of nearly 50 people a day continues, there will be 10,000 people in the "jungle" before the end of September, compared to just 6,000 in November last year.

Some residents have been there for more than a year. Most people in the camp are in tents and temporary accommodation.

Josie Naughton, co-founder of Help Refugees, said: "We expected the numbers not to increase too dramatically over the past month, as it is so difficult to travel during the holy month of Ramadan. However we are still seeing a persistent pattern of growth, which, if sustained, will amount to a population of over 10,000 come September."

She continued: "If the camp is set to be destroyed without adequate alternatives being offered to all residents currently without secured accommodation, many of whom have already been displaced at least once, then this is truly terrible news.

"More than a hundred children went unaccounted for the last time French police moved in to evict the camp. That is sure to happen again unless French and British officials work together to ensure that these children are protected, and that those who have the legal right to be reunited with immediate family in the UK have their cases expedited.

"There are 10,000 children who have reportedly gone missing in Europe so far. Another eviction could add hundreds more to that devastating tally."

At present, border checks are conducted on the French side of the Channel but post-Brexit, the Touquet agreement which covers this arrangement could be under threat.

Mayor of Calais Natacha Bouchart is calling for the agreement to be suspended.

She told French broadcaster BFM TV: "The British must take on the consequences of their choice.

"We are in a strong position to push, to press this request for a review and we are asking the President to bring his weight.

"We must put everything on the table and there must be an element of division, of sharing."

Earlier this week a Catholic priest reported finding one of two warehouses belonging to the charity Care 4 Calais empty and the other barely two thirds full after visiting the camp.

Father Dominic Howarth of Our Lady and All Saints, Basildon, said: "The warehouses are perilously empty. We have never seen it like this. It is a far, far cry from the time last September when donations were coming in faster than warehouses could be found. The aid now is only the raw essentials – and there is nowhere near enough to meet the needs."