The refugee charities who carried out the research are calling on the government to develop alternatives to custody for immigrants aged under 18.

The Refugee Council, Save the Children and Bail for Immigration Detainees said it was "inhumane and unnecessary".

They also want the Home Office to reveal exactly how many children are detained with their families.

The Home Office has in the past said that while detention was an essential part of an effective immigration system, it was used sparingly, especially when children were involved.

Bail for Immigration Detainees legal director Tim Baster told BBC News the immigration service could detain children for months at a time without going through the courts.

"We must speak out to defend these children, who are the only ones in this country who can be locked up without any legal process and without having committed any crime," he said.


These places cause a huge amount of emotional trauma, and they are definitely no place for a child
Refugee Council chief executive Maeve Sherlock

Centre 'damaging children'

"Detention of children is morally wrong and must stop immediately."

The charities are commissioning a joint report into alternatives to custody.

Refugee Council chief executive Maeve Sherlock said: "There are viable alternatives that are far less costly in both financial and human terms."

Immigration centres saw "a high number of cases of self-harm", she added.


This is no way to treat children
Save the Children chief executive Jasmine Whitbread

"These places cause a huge amount of emotional trauma, and they are definitely no place for a child."

Save the Children chief executive Jasmine Whitbread said child detainees suffered nightmares, depression and eating disorders.

"These already vulnerable children can find themselves forcibly removed from their familiar surroundings - home, school, friends, clothes and toys.
"They are locked up having committed no crime. This is no way to treat children."