Report highlights case of one expectant mother who collapsed during four-day journey from Northern Ireland to Bedfordshire

The detention of "too many" pregnant women at Yarl's Wood immigration removal centre has been heavily criticised by the chief inspector of prisons, Nick Hardwick.

Hardwick particularly highlighted the case of one pregnant detainee who had endured a four-day journey from Belfast to Yarl's Wood in Bedfordshire via Scotland and Manchester airport, where she had collapsed.

The privately-run centre was the scene of a major riot and fire in 2002 and is now the main detention centre for women facing deportation from Britain. At the time of the inspection in July, it held 229 women and 27 male partners. Children have not been held there since December 2010.

Hardwick said in a report published on Wednesday that there were seven pregnant women at Yarl's Wood at the time of his inspection, despite the fact that they should only be held in exceptional circumstances.

"We reviewed the UK Border Agency files for five of them. Only one of the monthly review letters mentioned pregnancy and even that one suggested that the pregnancy was disputed, although it had been confirmed for some time," the report said.

"Too many pregnant women, who should only have been held in exceptional circumstances, were detained in the centre," it said.

The report said that the pregnant woman subjected to a four-day journey to Yarl's Wood had initially been detained in Northern Ireland.

"From Belfast she had been transferred to Dungavel immigration removal centre in Scotland and then to Pennine House at Manchester airport, where she had collapsed. She had been taken to hospital and treated before completing the rest of her journey to Yarl's Wood, where she went through the detained fast-track process."

Hardwick said that in most other areas the detention centre had improved since its last official inspection in 2009, with a high proportion of detainees saying they were treated with respect by staff and with little evidence of bullying or women at risk of suicide or self-harm.

He did however criticise the fact that the number of female staff at the Serco-run centre was too low and said men were sometimes left in sole charge of units at night. Women complained that male staff sometimes knocked and then entered their rooms without waiting to be invited in.

Hardwick said: "Yarl's Wood is a unique facility dealing with sometimes very vulnerable women at a difficult time of their lives. Nevertheless, this inspection found evidence of some significant improvements.

"However, concerns remain, particularly about how the needs of vulnerable women are met."

Celia Clarke of the campaign group Bail for Immigration Detainees said they were gravely concerned about the chief inspector's findings. She described the four-day journey as "appalling practice by UKBA which put the health of women and their unborn children at serious risk" and as such was "wholly unacceptable".

She said ministers should end the unnecessary practice of holding pregnant women in immigration detention when there was scant risk they would abscond given their need for regular medical care.