Doubts over the value of a sex offender treatment course that black cab rapist John Worboys will have to complete have added to the controversy over his imminent release from jail.

Probation staff have been warned that community programmes designed to reduce offenders’ risk to women may not be as good as once thought, according to an internal letter seen by Sky News.

Worboys, 60, is expected to be freed soon after convincing the Parole Board he is no longer a threat.

The news caused a storm among his many victims, who were not consulted about his release and were originally assured by police that he would spend many, many years in prison.

He has served a year more than his minimum eight-year sentence for drugging and sexually assaulting his taxi passengers in London.

He was convicted of attacking 12 women, but dozens more allegations were never prosecuted.

Concerns over community rehabilitation have emerged months after the Ministry of Justice secretly scrapped the main programme for serving prisoners.

An in-house study showed the reoffending rate for those who took the course was higher than for those who did not.

It is believed Worboys started the now-discredited course in prison after years spent denying his crimes and challenging his conviction, before eventually applying and winning parole.

In a letter signed by a senior manager at the Prison and Probation Service, staff were warned about the community courses for freed prisoners.

It says: You should be aware that the international evidence to support the use of programmes for this group is not as strong as it once was.

The letter, sent last summer, reveals that the courses are to be replaced, just like the main prison treatment programme.

Former Probation Service trades union leader Harry Fletcher said that supervising Worboys’ release was becoming increasingly difficult.

Mr Fletcher, of the Victims’ Rights Campaign, said: With anybody with Worboys’ background released on licence, three things must come into play: conditions to protect him from vigilantes, keep him away from women, and address his behaviour.

Unfortunately, what the new evidence is now showing is that there are grave doubts about the ability of the community programmes to influence behaviour.

Worboys is still in jail, his release on hold while two of his victims and the Mayor of London begin a High Court bid to have his parole blocked.

The Metropolitan Police is also investigating a new allegation against Worboys from a woman who claims he assaulted her in 1997.

(c) Sky News 2018: ‘Grave doubts’ over cab rapist Warboys’ rehab course