Human Rights Watch on Tuesday condemned police abuse of migrants living in makeshift camps in France`s northern port city of Calais, from where they hope to cross to Britain.
The organisation also slammed the slow response of the French government to the poor living conditions of the migrants, whose numbers have swelled to over 2,000 in recent months.
"Asylum seekers and migrants shouldn`t have to face police violence in France, and no one who applies for asylum should be left to live in the street," said Izza Leghtas, HRW western Europe researcher.
HRW interviewed migrants and asylum seekers who described police abuse and attacks with pepper spray when they tried to hide in trucks as a means of smuggling themselves across the Channel, or as they walked in the town.
Rosa, 25, who said she was from Eritrea, told the rights body that police beat her up when they found her in a truck on the highway.
"The police checked the truck and found me," she said. "I said, `Please help me,` but they beat me and I collapsed outside the truck. They kicked me on the ground."
Salamou, 28, also from Eritrea, with visible injuries on his nose, said three police officers beat him up when he was just walking near a gas station.
"They kicked me on the ground, just like a dog," he said.
France has denied police abuse and Interior Minister Bernard Cazeneuve criticised HRW for "not taking time to verify" if the accusations made were correct.With its rail and sea links to the UK, Calais has long been a hub for migrants, but numbers have soared since spring 2014, as more and more people flee conflict and repression in Sudan, Syria, Eritrea, and Ethiopia.
An immigrant detention centre was shut down there in 2012 as the French and UK governments said it was luring migrants to the area.
Now the migrants -- including women and children -- sleep rough, making regular attempts to mob the port en masse to try and scramble onto trucks boarding ferries to Britain.
In the largest camp, which houses up to 900 people and is known as "the jungle", the migrants live in misery with no water, no sanitation, little to eat and in biting cold now that winter has set in.
A government-funded warehouse to shelter migrants only opens when the temperature drops below -5 degrees Celsius (23 degrees Fahrenheit), HRW said.
Tensions often boil over between the different nationalities, who battle for control of areas where they sleep, or choice spots from which to sneak into a truck.
Many migrants do not want to stay in France, as the asylum process can take over two years, and they have nowhere to live in that period.
They also cite police abuse and hostility from the local population, said HRW.