The chief inspector of prisons this week said children should generally no longer be detained in immigration centres amid growing concerns over their poor education facilities.
Anne Owers made the call as the Home Office revealed that the number of children held at UK detention centres increased this year, with more than a third detained for more than two weeks.
"In the enforcement of immigration control, I think children have become invisible," she said. "The focus is on the adults and what happens to them.
Children's needs are not taken into account."
Ms Owers' comments follow criticism last month of the Yarl's Wood unit, near Bedford, Britain's biggest immigration centre, where inspectors found a five-year-old autistic girl so badly neglected that she had not eaten properly for four days.
The inspectors said other children had been "damaged" by their experiences at the centre, which was ill-equipped to deal with special needs. Three children had been detained just days before sitting their GCSE exams.
In an interview with The TES, Ms Owers said that the findings at Yarl's Wood underlined "significant concerns" she had about the detention of any child at UK immigration centres.
Figures published by the Home Office this week show that, on June 25, 70 people under the age of 18 were being detained under Immigration Act powers. The number is up by 10 in comparison to the same time last year, reflecting a new hardline stance on immigration by the Home Office.
Statistics show that more than a third of children (36 per cent) were held for two weeks or more, in comparison with 16 per cent at the same time in 2004.
Ms Owers said: "Our view on the detention of children is that it should be exceptional and for the shortest possible period.
There are education facilities in all immigration centres which hold children but they are only satisfactory in the very short term.
"You are dealing with a group of children who can range from four to 16 - and a population which is moving about all the time - and what we have found is that the education that can be provided in those circumstances is at best only suitable for younger children."
She called for more rigorous independent checks to be carried out by social services officials before immigration authorities attempt to move any child into a detention centre.
This follows complaints that some children are picked up directly from schools or home and hauled straight into a secure unit without any screening.
Nora McKenna, education policy adviser for the Refugee Council, said:
"Schooling for many of these children is key to providing some sort of stability in their lives. It provides a daily routine, contact with other youngsters and of course access to learning, which is crucial if they are going to integrate into a new country."