Handing over victims and witnesses to the Home Office undermines fight against crime, say Liberty and Southall Black Sisters.

The first ever super-complaint to be lodged against the police will challenge the systemic and “potentially unlawful” practice of forces referring victims and witnesses of crime to the immigration authorities.

The complaint, to be formally issued by human rights groups Liberty and Southall Black Sisters, argues that handing over victims of crime to the Home Office for immigration enforcement undermines the fight against crime and erodes public safety. The “super-complaint” process became operational last month and allows designated organisations to “raise issues on behalf of the public about harmful patterns or trends in policing”.

The complaint will now be reviewed by senior officials from the College of Policing, the Independent Office for Police Complaints and Her Majesty’s Inspectorate of Constabulary and Fire & Rescue Services and could force changes to existing practices.

An investigation by Liberty exposed a secretive data-sharing arrangement whereby victims and witnesses of crime were frequently reported to immigration enforcement by police. Liberty and Southall Black Sisters say that this deters the reporting of offences and counters the police’s broader objectives, as well as obligation under human rights law to investigate serious crimes.

The two groups are presenting more than 50 pages of evidence and claim there needs to be guidance prohibiting data-sharing by all 43 police forces in England and Wales.

After learning that forces were likely to face a challenge over the issue, the National Police Chiefs Council (NPCC) issued new guidance last week. The new measures, agreed by police chiefs in England and Wales, include a ban on officers checking the police national computer solely to learn if someone has leave to remain in the UK.

However, lawyers for Liberty claim the new guidance does not go far enough to protect victims and witnesses of crime. Liberty solicitor Debaleena Dasgupta said: “Data-sharing undermines the police response to crime, which endangers us all by allowing criminals to act with near impunity. Rather than improving things, this practice is now encouraged in terms by the new guidance, despite the announcement last week – it is disingenuous of the NPCC to suggest otherwise.”

Critics say the policy has allowed criminals to use their victim’s immigration status so they can be coerced into not reporting offences. It means individuals may stay in situations where they are repeatedly abused or forced to participate in crime.

Announcing its revised guidance, the NPCC admitted the practice had damaged police’s standing in communities and may have dissuaded victims of modern slavery and trafficking from coming forward.

Dasgupta said: “The only acceptable solution is the formal creation of a firewall – a cast-iron promise that personal information collected about victims and witnesses by public services like the police will not be shared with the Home Office for immigration enforcement purposes.”

Pragna Patel of Southall Black Sisters described the practice as a direct outcome of the “hostile environment” policy: “We have seen the police repeatedly prioritise immigration enforcement, ahead of the wellbeing of some of the most vulnerable women who report domestic and sexual violence.

“Immigration enforcement is being conflated with safeguarding issues but let us be clear about this: reporting and detaining women or men as a ‘safeguarding’ measure is nothing of the sort – it is a violation of their civil and human rights. Immigration enforcement masquerading as ‘safeguarding’ heightens the multiple risks abused women face and re-traumatises them.”

The NPCC lead for immigration crime, chief constable Shaun Sawyer, said: “We have recently set out a clear position on exchanging information about victims of crime with immigration enforcement to encourage a consistent approach across the country. Chief constables have endorsed this position and are amending local policies accordingly. The police priority is to protect victims and investigate crime, and we are extremely careful about doing anything to deter victims from reporting to us.”