The mayor of Calais on Monday raised the prospect of bringing in the army to watch over a slum where some 6,000 migrants and refugees are camped out in dire conditions.

The so-called "New Jungle" camp, which is around an hour away on foot from the centre of the northern French port city, has swelled in size over recent months as more and more migrants arrive, wanting to cross over to Britain.

"Maybe the army should come to watch over the place," Natacha Bouchart told RMC radio, calling the camp a town "in which we don't really know what is going on".

"It would not be inappropriate to ask that the army come to supervise, reassure, and maybe dismantle some networks that may exist."

Some 750 police officers are already deployed in Calais and the surrounding areas, from where migrants and refugees from the horn of Africa, Middle East or Afghanistan try to cross to Britain onboard trucks, ferries or through the Channel Tunnel.

Tighter security has meant the number of illegal crossings to England -- which numbered up to 150 per day in August -- have slowed.

But many migrants and refugees remain in the "New Jungle" camp, whose winding slum-like alleys are dotted with crude shelters made of wood and salvaged material.

As the cold weather arrives, humanitarian organisations fear that conditions for the thousands of migrants will worsen.

Adding to this, documents seen by AFP show the camp is located next to two chemical factories that are classed as high-risk for the toxic substances that are used and stored there.