Yarl's Wood detention centre in Bedfordshire, remains "no place for a child", the children's commissioner for England has said in a new report published today.
Sir Al Aynsley-Green said that although some conditions have improved since 2008, detention at immigration removal centres is still "distressing and harmful" to children, and that he wants to see an end to the practice.
He highlighted in particular loud or violent arrests, separation from parents, and a lack of information.
In one case a family was held for 70 days, Sir Al's progress report found. More than 1,000 children are detained every year, for an average of about two weeks, according to official figures.
Sir Al demanded reviews of welfare and healthcare protection procedures, describing systems to safeguard children, and a lack of paediatric expertise, as "high-risk".
He cited the case of a five-year-old girl waiting 24 hours for hospital treatment because a nurse failed to diagnose a broken arm from a fall in the centre's playground.
Sir Al said: "Ultimately, I would like to see a far faster process and an end to the detention of children in the asylum system.
"But I recognise an end to child detention won't happen overnight.
He praised the UK Border Agency for stopping the use of caged vans to transport children to the centre, but also said that this may have had the unintended consequence of separating parents and children, as more were now transported in separate vans.
Among the children's complaints were that arresting officers acted in a "terrifying" way, "bashing and kicking" at doors, were "rude" and watched as youngsters used the toilet or dressed.
Churches and other faith groups are amongst those who are campaigning for en end to child detention. Last Christmas, the Rev Professor Nicholas Sagovsky, Canon Theologian at Westminster Abbey, was prevented from delivering presents to children at Yarl's Wood.
A Home Office Minister, Meg Hillier, said that treating children "with care and compassion is an absolute priority for the UK Border Agency".
She added: "We take the detention of families very seriously. We believe that children should not be separated from their parents.
"We always release families where advised it is in their best interests by independent social workers and specialist medical professionals.
"We only detain families when the independent courts conclude they have no right to remain in the UK. We encourage families to return voluntarily, avoiding the need for detention. If they refuse to return, we have no choice but to enforce their removal."
Lisa Nandy, from The Children's Society, added: "It is outrageous that children in the UK are subject to such inhumane treatment at the hands of the state."
Sir Al and his team used documentary evidence, visits and interviews with detainees to come to their conclusions.
Ekklesia is a member of Still Human Still Here the campaign to end the destitution of refused asylum seekers.