The new guidelines, which come into force on September 1, compel convicted paedophiles to tell the police when they move in or out of an area - on pain of a Pounds 5,000 fine or a six-month jail sentence. Schools are also expected to be informed if a paedophile has moved into the area.
The register has been welcomed by the police, child protection charities and probation officers.
Psychologists at the Young Abusers Project in London are looking at how people become paedophiles and attempting to change abusive behaviour before it becomes entrenched. According to Jane Millarini, clinical practice manager at the YAP, many people have difficulty acknowledging that very young children can be the perpetrators of sex abuse as well as victims of it. The clinic's youngest client is eight, and children of three can exhibit highly sexualised behaviour, copied from adults.
Adult paedophiles are very difficult to treat, but, says Ms Millarini, "young people have the capacity for change, and they are less likely to be in denial of what they do".
The clinic, supported by the National Society for the Prevention of Cruelty to Children, treats 160 children and adolescents with a combination of group therapy and individual psychotherapy. The majority have been abused themselves, and the average age for the onset of abusive behaviour towards other children is, disturbingly, coming down - it is now 14, compared with 16 or 17 when the project started five years ago.
The therapy involves persuading the young people to confront what they have done and to encourage them to empathise with their victims, which is particularly difficult for children who have been victims themselves. The children, says Ms Millarini, are usually "relieved to find out that they are not unique". They are also aware of the public view of paedophiles, which can motivate them to change their behaviour. Adult paedophiles, by contrast, are more practised in the art of self-deception and will not recognise themselves as abusers.
According to Ms Millarini, there is a professional reluctance to label children as abusers too young "for fear that it might set them on a career path. The majority are cautioned, or not even that. The problem with this is that the child may get the idea that what they did, did not really matter. "
Many adults do not want to believe that very young children are capable of abuse. "They prefer to see it as exploratory behaviour, like playing doctors and nurses. But a child of five or six can do a lot of damage to a younger child. Boys are technically capable of rape or serious sexual assault when very young." A surprising amount of sex abuse, she says, is committed by older children on younger ones - babysitters, cousins, or neighbours.
Ms Millarini is also concerned that the Sex Offenders Register may make undetected paedophiles more reluctant to seek help for fear of being hounded out of an area.