Children held at Britain’s largest immigration detention centre are being “damaged” because of their incarceration, the prisons watchdog said on Wednesday.

A report by Anne Owers, the Chief Inspector of Prisons, said inadequate procedures and the effect of detention itself at the Yarl’s Wood centre in Bedford, north of London, had a negative effect on children.

She cited the case of one five-year-old autistic girl who had not eaten properly for four days when inspectors visited.

“We were particularly concerned about the welfare of some of the children who were detained,” the report said.

In another case three children were held just before taking their GCSE exams.

“Two of those children were released following the inspection: but the damage had already been done and the systems in place were simply inadequate to pick this up routinely,” Owers said.

Yarl’s Wood, which can house up to 900 inmates including failed asylum seekers and their families before deportation, was partly burnt down when inmates rioted in 2002.

Since reopening it has become the main removal centre for women and children.

Owers said detainees were twice as likely to feel unsafe at Yarl’s Wood as at other detention centres and the education provisions were inadequate especially for older children.

“This underlines the recommendation we have repeatedly made: that the detention of children should be exceptional and there must be independent and immediate welfare and needs assessments of each child,” the report said.

Home Office minister Tony McNulty said the report had recognised that work had been done to make the centre child-friendly.

“We recognise that detention of families with children is an emotive issue and it is not something we do lightly,” he said.

“Detention is used sparingly and for the shortest period necessary. However, the power to detain is an essential part of protecting the integrity of and public confidence in our immigration controls.”

The Refugee Council said the report was “disappointing and revealing”.

“The report is clear that detention, however well done, harms the welfare and development of children,” the council’s Tim Finch said.

Campaign group Legal Action for Women said more than 30 Ugandan women had gone on hunger strike at the centre but Yarl’s Wood authorities have denied this.