A voluntary programme offering libido-suppressing medication to sex offenders in England and Wales could be rolled out nationally by December 2028, an expert has said, as the pilot scheme doubles from ten to twenty prisons this November amid government efforts to ease prison overcrowding.
Thousands of male sex offenders in England and Wales could be offered libido-suppressing medication under government plans to expand a voluntary treatment programme nationally by December 2028, according to Professor Belinda Winder, who has evaluated the use of the drugs in prisons. Winder said around one in four sex offenders, equating to 3,750 current prisoners, would be considered for the treatment. Government sources have told the Guardian that Andy Burnham’s administration is keen to expand the scheme amid ongoing efforts to ease the prison overcrowding crisis.
What the pilot involves
The pilot programme, known as the medication to manage problematic sexual arousal treatment pathway (MMPSA), began in four prisons across the south-west of England before expanding to ten. It will grow further still, to twenty prisons, this November, extending into two additional NHS regions covering the north-west and north-east of England.
The scheme is designed for sex offenders who experience intrusive, persistent and intense sexual thoughts, along with persistent arousal and unhealthy sexual urges and behaviours. Participants can be offered selective serotonin reuptake inhibitors (SSRIs), such as sertraline, which help limit invasive sexual thoughts, as well as anti-androgens, which reduce testosterone production and limit libido, in some cases reducing testosterone to pre-pubescent levels.
The government has confirmed that the medication can also form part of an offender’s support after release, working alongside psychological treatment and supervision, meaning the programme is not intended to end automatically once someone leaves prison. Officials have previously said the expanded programme could ultimately make treatment available to around 6,400 sex offenders, a considerably higher figure than the 3,750 currently in prison estimated by Winder, once those able to access treatment after release are included.
A possible timeline for national rollout
Winder said officials could be in a position to launch the programme across prisons and probation services throughout England and Wales within 28 months, provided the pilot continues to progress well. “They [the Ministry of Justice] could be ready in December 2028 to roll the programme out if the interim findings look useful,” she said.
However, it is worth noting that this timeline is not yet a confirmed government commitment. A government-backed research project examining professional views of the MMPSA programme was still recruiting participants at the time of reporting, meaning further evidence about how clinicians and other professionals assess the treatment continues to be gathered, and the December 2028 date remains contingent on that ongoing evaluation.
Winder stressed that any national rollout would need to be properly resourced and supported. “I am optimistic that a properly resourced, voluntary national MMPSA pathway could ultimately be developed… A good national service needs appropriately trained clinicians, clear referral routes, appropriate psychological support alongside medication,” she said.
Doubts remain over mandatory treatment
Separately from the voluntary pilot, ministers have continued to examine whether treatment could eventually be made compulsory for certain offenders. Last year, then justice secretary Shabana Mahmood told MPs she was exploring a national rollout of voluntary chemical castration, alongside the possibility of making it mandatory. In a parliamentary answer, the Ministry of Justice said it was still examining the possibility of compulsory treatment in future.
A proposed amendment to the Sentencing Act 2026 called for the government to publish a report within a year examining how mandatory chemical suppression could be introduced for certain sex offenders, alongside appropriate legal and clinical safeguards. However, Parliament had not yet considered the amendment at the time of reporting.
Winder, who is co-chief investigator of a Prozac clinical trial involving sex offenders, voiced significant concerns about a mandatory approach. “A mandatory approach would require screening a very large prison population to identify the much smaller group for whom treatment might actually be appropriate,” she said. “It would have substantial clinical and resource implications.” She also warned that imposing the treatment could damage trust between offenders and clinical staff, and could be open to abuse. “Trying to impose and monitor daily medication among people who do not necessarily want to take it could be extremely inefficient. It could also introduce a range of consequences that we simply do not yet understand, including effects on trust, disclosure, engagement and the therapeutic relationship.”
Winder also pushed back on the term “chemical castration” being used to describe the drugs. “People say that because some people like the idea of castrating people who commit sexual offences,” she said. “But these drugs are not permanent, unlike castration, and must be taken consistently to work.”
Health risks and safeguards
The Ministry of Justice has acknowledged that anti-androgen drugs can carry serious medium- and long-term health risks, meaning prisoners receiving them require careful clinical monitoring throughout treatment. Officials have stressed that the medication is intended specifically for offenders whose behaviour is linked to persistent sexual thoughts, compulsive sexual behaviour or problematic sexual arousal, rather than being considered automatically suitable for everyone convicted of a sexual offence. The government has also emphasised that medication is intended to be used alongside psychological interventions, including accredited offending behaviour programmes, therapy and probation supervision, rather than functioning as a standalone treatment.
Government guidance has indicated that victims would not automatically be informed whether an offender is taking libido-suppressing medication, since treatment information is protected by medical confidentiality. Victims eligible for the Victim Contact Scheme can still receive information about an offender’s release and request specific licence conditions.
Context: prison overcrowding and early release
The scale of the challenge facing the justice system is significant: around 15,000 prisoners in England and Wales are currently serving sentences for sexual offences, and more than 850 men a month are arrested on suspicion of online child sexual abuse offences.
Earlier this month, Burnham announced that prisoners convicted of rape, grooming and serious child sexual offences would be excluded from the early release scheme due to begin in October, though other sex offenders serving sentences of less than four years will remain eligible for early release. In Parliament in July, the government described the expansion of chemical suppression as part of a wider package that also includes increased investment in probation, expanded electronic tagging and tighter restrictions on offenders following release.
Reoffending rates among sex offenders remain comparatively low relative to other groups of offenders. According to government data, 11.7% of sex offenders reoffended in 2023, compared with 53.9% of those whose index offence was theft.
Caution from campaigners and unions
Prison reform campaigners have urged caution before any national rollout proceeds. Critics have previously noted that long-term testosterone suppression can cause osteoporosis and cardiovascular disease, though data remains limited due to a scarcity of randomised controlled trials in this area.
Andrew Neilson, director of campaigns at the Howard League for Penal Reform, said: “The history of prison-based treatment programmes in this area has proven troubled, which is both a reason for exploring alternatives but also a reason to exercise caution before expanding new approaches more widely. It’s also important that nobody is forced into these chemical interventions and that participation is truly voluntary.”
Mark Fairhurst, national chair of the prison officers’ union the POA, offered a more cautious welcome, saying: “Anything that potentially protects the public is welcome but I would be cautious about the rollout until we are in receipt of evidence that proves success.”
A Ministry of Justice spokesperson said: “This government is determined to tackle the root causes of sex offending, which is why we’re working at pace to extend the existing pilot to a further two regions.”
