Conditions at a French refugee centre in Dunkirk are so dangerous that adult nappies are amongst the most requested items among people stranded there.
"Women are too scared to go to the toilets in the night. None of the locks in the women's toilets in the camp work," a camp volunteer coordinator said.
Women and children are allegedly being raped by traffickers at a French refugee camp in return for blankets and food, according to volunteers and officials.
Legal proceedings will be sent by Bindmans against the Home Office which is accused of acting unfairly by electing to settle only minors from the Calais camp that closed in October 2016.
British MP Theresa May was sent a petition of 50,000 signatures by Labour peer Alf Dubs on Saturday (11 February), in anger at the government's decision to end the Dubs scheme.
"Our clients call upon the home secretary to reconsider her position," Caroline Robinson of Bindmans said.
Only 350 refugee children entered the UK, 10% of the number that MPs had been led to believe could enter.
A volunteer coordinator, who has worked at the Dunkirk camp told the Observer: "Sexual assault, violence and rape are all far too common. Minors are assaulted and women are raped and forced to pay for smuggling with their bodies."
Speaking on condition of anonymity, she said: "Although the showers are meant to be locked at night, particularly dangerous individuals in the camp have keys and are able to take the women to the showers in the night to force themselves on them. This has happened to women I know very well."
The failure of authorities to guard the Camp de la Linière – the Dunkirk Camp – has resulted in smugglers taking control, say The Dunkirk Legal Support Team. Testimonies collated by the Observer describe appalling living conditions and an atmosphere of intimidation.
The volunteer said: "A 12-year-old girl was groomed in the camp by a man well over twice her age. When she no longer wanted to speak with him because his behaviour towards her had become so obscene, he threatened her. A 13-year-old boy ended up returning to his home country having been raped in the camp."
The revelations come as other health experts have revealed that teenaged migrants are raped so frequently by people traffickers, traffickers give girls as young as 13 dangerously high doses of injected contraceptives to stop them getting pregnant.