In 2017, the government's flagship treatment scheme for people convicted in England and Wales of rape or child sexual abuse was scrapped after it was shown to raise the risk of reoffending. Two sex offenders have told BBC Radio 4's File on 4 programme what it was like to take part in the rehabilitation programme.
"Everything was discussed in minute detail. They had what was called the 'hot seat' and every prisoner that was in a group had to sit in the hot seat and they were bombarded - it was like an interrogation."
These are Paul's experiences of group sessions on the discredited Sex Offender Treatment Programme (SOTP), which ran from the early 1990s until 2017.
Paul has been convicted of numerous offences, including rape, and is serving a long jail sentence.
Speaking to me from a prison pay-phone, he says he started the SOTP on three occasions - it was a cognitive behaviour therapy designed to teach offenders to think and act differently.
But, the 60-year-old says, each time, he was removed from the course before the end because group facilitators thought he "wasn't learning anything".
"Being in group settings, discussing serious offences and some less serious offences - because these groups were mixed - actually made prisoners worse and normalised what prisoners were doing," he says.
Rapists, murderers, child sex offenders and "flashers" were all placed together, says Paul.
"People were learning from their mistakes - they were learning from other group members how to perhaps be better sex offenders without being caught."
Ministry of Justice (MoJ) research showed 10% of men who had completed the SOTP reoffended, compared with 8% of those who had not done the programme.
The results were published five years after analyst Kathryn Hopkins first alerted the department the scheme might not be working.
Paul also claims some inmates were told to disclose the names of their victims as part of the process of setting out their offending history in graphic detail.
"It was to physically humiliate you and break you - I could see no other purpose for it," he says.
Many of Paul's observations are shared by Dr Robert Forde, a retired forensic psychologist who used to work for the Home Office and is an expert on assessing risk.
Dr Forde told File on 4: "One prisoner said to me, 'I hate doing this course because I've never had so many deviant sexual thoughts as I've had since I started because we're talking about sex offending all the time and actually I want to get away from all that.'"
Another prisoner, who had himself been a victim of sex abuse as a child, told him he had been asked to give details of what had happened to him in front of paedophiles who had became aroused as a result.
Dr Forde said some prisoners on the SOTP courses would "play the system" in order to convince the Parole Board they were safe to be released.
He said one prisoner had told him: "You claim to have things like deviant thoughts about victims or indulge in deviant sexual practices and then after the course is finished and you're doing the post-course assessment, you then drop all these things and you just tell the truth."
The inmate claimed this would then result in the prisoner being given a lower risk score by course assessors.
Former prisoner Peter, who has served two sentences for sexual offences against children and possessing indecent images, tells me the SOTP provided a false sense of security.
"You come out thinking you're fixed," he says.
"There's that feeling... because it's a treatment programme and that's what treatment does, doesn't it - fixes what's wrong?"
Now in his 50s, Peter had to do a "booster" course when he was first released.
"You're going back over the offences, so you keep reliving this stuff that just isn't helpful," he says.
"You're not going to forget what you've done and you know you've made victims... if you're going to be a useful member of society, you need to try and move your life forward."
During his second spell in jail, Peter completed one-to-one sessions as part of the Healthy Sex Programme, which he found far more beneficial because it focused less on his offending and more on steps to overcome his problems.
He is now receiving support at the Corbett Centre, a groundbreaking project in Nottingham run by the Safer Living Foundation Charity.
It provides a range of emotional help and practical support for about 30 sex offenders living in the community.
"You're in an environment where people know what's happened," Peter says.
"So you're not having to start your life with a lie... you can put your life back on track."
Although the Corbett Centre shows some promising early signs, it will be some years before it is known whether it reduces reoffending in the long term.
A number of Ministry of Justice initiatives are also unproven - the Healthy Sex Programme is currently being evaluated, while the two sex offender rehabilitation schemes that replaced the SOTP, Horizon and Kaizen, have yet to be tested.
The MoJ says it works "closely" with the Correctional Services Accreditation and Advice Panel in the design of programmes delivered in prison and on probation.
The department says the panel, which has to approve such schemes before they can be used, is made up of "independent experts from academia and practice from across the world".
But two forensic psychiatrists, Penny Brown and Callum Ross, have been so alarmed by the failings in the SOTP programme they are calling for greater oversight of new forms of treatment.
This week, the Lancet Psychiatry medical journal published a paper they have written.
"We want to get reassurance that government-funded policy research is subjected to the same requirements and high academic standards that are placed on everybody else and all other scientists," says Dr Brown.
"The need to show that you're doing something shouldn't override the risk of actually causing harm."