Two-thirds of women held at a controversial immigration removal centre are later released into the community, a watchdog report reveals.
Inspectors said the finding raised questions about the justification for detaining them at Yarl's Wood in the first place.
The facility near Bedford houses adult women and family groups, as well as a small number of men who arrived in Britain as "clandestine migrants" on freight lorries.
At the time of the assessment by HM Inspectorate of Prisons (HMIP) in June, more than 300 people were being held at the centre.
The inspection report disclosed that during the previous six months, excluding men, 542 (21%) detainees had been removed from the centre, 295 (12%) had been transferred to other places of detention and 1,721 (67%) had been released.
It said: "During the previous six months, 67% of women had been released into the community, which raised questions about the justification for detention in the first place."
Fewer detainees than at the previous inspection were being held for very long periods, the watchdog noted.
At the time of the latest visit, none had been held for over a year, although 14 had been held for between six and 12 months.
The inspectorate said the handling of cases by the Home Office was a "principal area of concern".
It found that delays and uncertainty in the outcome of immigration casework were still a cause of frustration and anxiety for detainees, some of whom had been held for too long.
The quality of assessments of vulnerable detainees have improved but not by enough, the report said.
Inspectors raised concerns over the continued detention of women who had been tortured and two responses where the Home Office had refused, without explanation, to accept that rape came within the legal definition of torture.
Yarl's Wood (pictured) has repeatedly come under scrutiny since it opened in 2001 and was labelled a "place of national concern" two years ago.
The 2017 inspection found there had been "significant improvements" at the centre, which is operated by Serco.
There was little violence and the atmosphere was far calmer, more respectful and relaxed, HMIP said.
A Home Office spokewoman said:"Detention and removal are essential parts of effective immigration controls.
"It is vital these are carried out with dignity and respect and we take the welfare of our detainees very seriously.
"We welcome the Chief Inspector of Prisons' recognition that improvements have been made at the centre and we are taking action to address the recommendations."
Serco, which is not responsible for determining policy on immigration detention or individual decisions regarding the length of detention, welcomed the report's recognition of progress made since the last inspection.
Steve Hewer, Serco contract director for Yarl's Wood IRC, said his team of staff have "worked tirelessly over the past two years to continuously improve our performance at the centre, often in challenging circumstances".
He added: "We are committed to further building on this progress as we continue to focus on providing a caring, safe and supportive environment for all our residents."
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