A woman who was trafficked into Britain for prostitution and later locked up in an immigration centre is entitled to substantial damages from the Home Office for unlawful detention, the high court has ruled.

The woman, identified only as ZV, reported being beaten, forcibly injected with heroin and forced into prostitution for eight years by an abusive partner who initially targeted her in Lithuania in 2009.

The case illustrates the predicament of trafficking victims who sometimes end up being imprisoned. The Crown Prosecution Service has issued guidance advising prosecutors to check whether cases should be discontinued.

ZV, now 34, said her former partner – referred to as DE – drugged and brought her to the UK, where she was “locked in a house … forced into prostitution and raped repeatedly by different men”.

She said she was later allowed to leave the house “but only to shoplift for [DE”, for which she was convicted five times between 2010 and 2012.

ZV then began a relationship with another woman she met in prison and they “ran away together” to Lithuania, believing DE was in prison in the UK.

But, she claimed, they were spotted by DE’s associates in Lithuania, kidnapped and gang-raped, before DE arrived and threatened to kill her unless she returned to the UK.

ZV said she was brought back to the UK to resume captivity and forced prostitution for a further four years until, in 2017, DE was deported.

She was imprisoned in June 2017 after being convicted of cannabis possession. She was transferred to Yarl’s Wood immigration removal centre in Bedfordshire pending her proposed deportation, and was held there for five months.

Delivering judgment on Thursday, Mr Justice Garnham said ZV was entitled to substantial damages for 45 days’ unlawful detention rather than her entire period at Yarl’s Wood.

The Home Office had decided there were reasonable grounds for believing ZV was a victim of trafficking and took steps to secure appropriate accommodation for her release, which was approved on 13 October 2017. She was not, however, transferred to a safe house until 30 November after the high court ordered her release.

Garnham said: “There was an obligation on the secretary of state, in my judgment, urgently to take the steps necessary to effect her release. I can detect no such urgency. On the contrary, the impression with which I am left is of a marked reluctance to complete the necessary process.”

The judge added that he considered it “revealing that once a court ordered release, the process was completed promptly”. He rejected ZV’s argument that the whole of her five-month detention was unlawful.