A Bail for Immigration Detainees (BID) study found that 200 children have been separated from their parents between 2009 and 2012 by the UK Border Agency.
The charity’s report found that these children suffered adverse effects including weight loss, nightmares, insomnia and “extreme isolation”.
Most of the children stayed with another family member or guardian, but 85 were taken into care when a single parent was detained.
The report found that children endured emotional distress in both scenarios and some of those put into care were “moved between unstable care arrangements, neglected, and placed at risk of serious harm”.
The 111 parents involved were detained for an average of 270 days, but in 92 cases the parents were eventually released.
In 15 cases, parents were deported or removed from the UK without their children.
BID said the plight of children separated from their parents contradicted Section 55 of the Borders, Citizenship and Immigration Act 2009, which placed a duty on the Border Agency to safeguard and promote the welfare of children.
The charity said the government should end the separation of families by immigration detention and, in the meantime, introduce a time limit for how long families can be separated for.
Sarah Campbell, research and policy manager at BID, described the situation as a “hidden scandal”.
“Children we spoke to described their despair and misery at not knowing if or when they would see their parent again,” she said.
“The Border Agency displayed a callous indifference in continuing to detain parents, in some cases despite having clear evidence that children were in wholly unsuitable care arrangements.
“The government must immediately end the inhumane practice of separating children from their parents for immigration purposes.”
BID said there are likely to be more cases of children being separated from their parents in the future since legal aid for most immigration cases was scrapped at the start of April.
The Home Office has been contacted for comment.