As a part of a voluntary scheme, sex offenders in Britain have been given drugs that reduce sex drive and make it difficult for them to re-offend, according to the Ministry of Justice.

Up till now, 11 men have put themselves forward for the pioneering project, which has been dubbed "chemical castration."

Those receiving the treatment include prison inmates and offenders who have been released from custody and are living in the community, the Telegraph reported.

The volunteers are being given Prozac, which lowers libido, or other categories of drugs known as anti-androgens.

The current project, which is being overseen by Professor Don Grubin, a forensic psychiatrist at Newcastle University's Institute of Neuroscience, could be the first step towards wider use of the technique.

However, experts have warned that it could prove impractical to impose the medication on sex offenders in a compulsory programme.

Prof Grubin said: "I am suggesting that consideration should be given to a formal national clinic. We are in the early stages of that and have had preliminary discussions with ministers about it.

"I certainly think it would be a benefit. A national clinic would work on prescribing and monitoring protocols and allow psychiatrists to gain a second opinion from me."

Professor David Wilson, a criminologist from Birmingham City University, warned that chemical castration should not be regarded as the solution to all types of sex offending.