It came as MPs and campaigners called for imposing a time limit on detention.
Migrants can be held indefinitely in prison-like immigration removal centres before being deported.
Around 30,000 people are detained in these centres every year. They are often refugees whose asylum requests have been turned down, or long term residents of Britain whose visas have run out.
Yarl’s Wood is the centre where women and family groups are detained. The watchdog HM Inspectorate of Prisons went there in June and released its report this week.
It found that two thirds of women held at Yarl’s Wood had been released back into the community rather than deported. This “raised questions about the justification for detention in the first place”.
There have been repeated cases of Yarl’s Wood detainees being abused by staff, from racist insults to sexual assault and harassment.
The inspection found some improvements since a 2015 inquiry following the allegations—detainees on suicide watch are no longer watched by male staff, for example.
But chief inspector Peter Clarke warned that victims of torture and rape were routinely being detained.
Medical assessments are supposed to spare from detention those, including torture victims, who would be harmed by being locked up.
But inspectors found cases where little medical evidence had been given to back up the decision to detain women who had been tortured.
One former detainee at the lobby called detention “a filing cabinet for human beings”
In two cases officials had refused to accept rape as coming within the definition of torture.
Clarke also called for a strict time limit on detention. At the time of the inspection 15 women had had been in Yarl’s Wood for more than six months—and one for more than three years.
A time limit was also one of the central demands of campaigners and MPs at a parliamentary meeting on detention on Thursday.
Scottish National Party MP Stuart McDonald said that if a vote were to be held now, a majority of MPs would support a time limit.
Labour MP Catherine West has tabled an early day motion to end indefinite detention—something every MP should be pressured to support.
But even with a time limit there’s no excuse for locking up refugees and migrants.
One former detainee at the lobby called detention “a filing cabinet for human beings”. These refugee prisons need to be shut down for good.