Charity Howard League for Penal Reform has sent a letter before claim to Justice Secretary Shabana Mahmood urging her to withdraw the decision.
The Government is being threatened with legal action over plans to allow prison officers to use synthetic pepper spray in young offender institutions.
Charity Howard League for Penal Reform has sent a letter before claim to Justice Secretary Shabana Mahmood urging her to reverse the move set to be rolled out this summer.
Pava spray, which is an incapacitant, is due to be made available “in limited circumstances” to a select number of specialist staff at the three public sector YOIs holding under-18s – YOI Werrington, Wetherby and Feltham A, the Ministry of Justice announced in April.
The measure, which seeks to combat rising violence from inmates, was welcomed by union bosses who lobbied for the change for prison officers to be given equipment to protect themselves.
The latest figures from the Ministry of Justice show rates of assaults on staff in the YOIs are 14 times higher than within adult prisons.
But the plan sparked criticism from the Children’s Commissioner and the charity, which warned it was “a serious escalation in the use of force that is permitted against children”.
The spray is set to be rolled out for an initial 12 months before it is reviewed by ministers, while each use of the spray will be reviewed by an independent panel.
On Tuesday, charity chief executive Andrea Coomber KC said: “The Howard League has been preparing to take whatever steps necessary to challenge the roll-out of Pava spray to prisons holding children, including potential legal action.
“We know that Pava spray has been used inappropriately in prisons holding adults; to use it on children would be catastrophic.

“Far from keeping children and staff safe, normalising the use of violence in this way risks making conditions even worse for those living and working in prison.”
The national charity is concerned there is a lack of research on the use of the spray in custody, and specifically against children, while existing research in relation to adults shows a “myriad of potential physiological health impacts”.
Ms Coomber added: “Instead of arming staff, the way to reduce violence is to close failing young offender institutions and ensure that children are accommodated in more appropriate settings – such as secure children’s homes – where they can be given the care and support they need. Prison is no place for a child.”
The pre-action letter sent by lawyers on behalf of Howard League asks for the Justice Secretary to withdraw the decision and respond within 14 days, it said.
The campaigners have also launched a crowd fundraiser to help them fund the challenge, which has currently raised more than £10,000.
Announcing the roll-out in April, justice minister Sir Nic Dakin said: “This Government inherited a criminal justice system in crisis. The unacceptable levels of violence faced by our brave frontline officers in young offender institutions is yet another symptom of that.
“This is not a decision we have made lightly, but our overarching duty is to keep staff and young people in custody safe. This spray is a vital tool to prevent serious violence, helping staff to focus on rehabilitation as part of our Plan for Change.”
The rate of assault incidents on staff last year was 170.0 per 100 children and young people at Feltham, 182.9 per 100 at Werrington, and 167.4 per 100 at Wetherby, Ministry of Justice figures show.
The rates are around 14 times the equivalent figure in adult prisons in England and Wales, which was 12.2 per 100.
The Ministry of Justice has been contacted for comment.