Treating sex offenders with chemical castration is to be reviewed by the Scottish Government amid a clamour to increase its use after the row over the planned release of rapist John Worboys.

Westminster Justice minister Phillip Lee has asked officials to consider increasing the deployment of anti-libidinal drugs following the furore on the black cab rapist’s parole.

It has been reported Dr Lee, a practising GP, has said that there needs to be “an evidence-based approach” to making offenders safe enough to release in society.

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It comes in the wake of the John Worboys scandal after the High Court overturned a decision by the parole board to release the former taxi driver and convicted rapist.

In Scotland the drugs are only offered to sex offenders on a voluntary basis. They act to suppress sexual urges and the ability to act on such impulses although evidence for their effectiveness is mixed.

Last year, the Glasgow Health and Social Care Partnership said it was carrying out a pilot scheme to trial the use of the drugs with sex offenders living in the community.

They said the drugs would be used on a case by case basis, when appropriate.

Now the Scottish Government is to publish new rules for doctors. social workers and prison officers on the wider use of the drugs.

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A spokesman said: “There is already a well-established procedure for the prescription of anti-libidinal drugs in Scotland which are only appropriate for a very small number of sex offenders and are used on a voluntary basis. This practice is currently under review and draft updated guidelines will be published shortly.”

He said minsters wanted to update the existing guidance on the medical treatment of sexual offenders – which came out in 2010. This says anti-libidinal drugs can reduce testosterone levels in offenders to those found in pre-pubescent boys, “thereby decreasing sexual interest and arousal”.

There are around 120 convicted sex offenders receiving libido-suppressing medication in England, a figure which Phillip Lee is said to want to increase tenfold. The Scottish Government said it was not known how many offenders in Scotland are agreeing to take the drugs.

Although offenders can still be sexually aroused, they are generally less interested in sex and there is “a great reduction in spontaneous sexual behaviour”.

However it warns that the drugs can take a number of months to work, and are not intended to be the sole form of treatment for sex offenders.

An alternative – using anti-depressants such as SSRIs – is also advocated to reduce the intensity of sexual fantasies and sexual urges”, to enable the offender to control them better. However the guidance adds: “This is not a predictable effect.”

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Following the publication of the 2010 guidance the Scottish Government established a network of psychiatrists to assess sex offenders for possible treatment. The current rules say chemical methods should not be the sole form of treatment and should instead be used as part of a wider psychological treatment. However they should be considered when offenders are preparing for release into the community, particularly where other methods have failed to control “hypersexual arousal,” or “deviant fantasies and arousal”.

The spokesman said the review would not make chemical castration compulsory, but would aim to look the evidence to see which offenders it should be offered to.

The move comes amid concern about the conviction and subsequent release of large numbers of sex offenders. Recorded sexual crime has been on a long-term upward trend for more than 20 years and increasing numbers of offenders are being convicted and released into the community.

While sex offenders have a lower rate of reoffending than those convicted of many other crimes, the success rate of programmes attempting to reduce the rate at which sex offenders reoffend has been poor.

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This programme, Moving Forward, Changing Lives, which is used both with inmates held in the Scottish Prison Service and with those managed by police and social services in the community, aims to work with convicted sex offenders on a largely psychological basis.

A spokesman said it aimed to tailor help individually to sex offenders who are asked to admit their behaviour and look at ways of changing it. He said: “We have established an intervention programme which encourages sex offenders to help prevent them from committing similar crimes.”