Police last night insisted their decision to caution rather than prosecute a sex offender who subjected a mentally ill man to an horrific attack was made in the best interests of the victim.

Police last night insisted their decision to caution rather than prosecute a sex offender who subjected a mentally ill man to an horrific attack was made in the best interests of the victim.

Although Mark Raynsford, 43, from Green Lane, Bradwell, near Yarmouth, will be placed on the sex offenders' register, he will not face a court appearance or further punishment after admitting luring a vulnerable victim to a house in Norwich where he was forced to have sex with a prostitute.

The decision was taken by officers in consultation with the Crown Prosecution Service and the victim. The force pledged that all possible avenues had been explored before deciding not to proceed to court and that careful consideration had been given to the victim's condition.

The chief executive of Norfolk Victim Support described the caution an “extraordinary action” and said it was important the public knew proper procedures had been followed.

It follows controversy last month after it emerged almost 8,000 sex offenders have been cautioned across England in the past five years, rather than being charged.

Brian Butcher, from Victim Support, said: “It is difficult to know why the police chose to take this course of action without knowing the full facts of the case.

“In cases in which there is a vulnerable victim there are various avenues, such as the use of intermediaries or video evidence, which can help bring the case to court, and I would hope these were considered.

Specialist adult protection social worker Kelly O'Donovan said: “The victim has been horrifically traumatised by this incident and continues to need support.”

Miss O'Donovan said she was pleased with the result of the case, saying it was a testament to the joint commitment of agencies in Norfolk to protecting vulnerable adults.

Det Con Dean Harrison, from the specialist adult protection unit which led the investigation, said: “We take these complaints very seriously and work in partnership with our colleagues from Norfolk Social Services in a specialist unit to safeguard the rights of vulnerable adults.”