The black-cab rapist John Worboys has been handed two additional life sentences for attacks on four more women as it was revealed the serial sexual predator confessed to targeting 90 victims.

The 62-year-old, who is already in prison for attacks on a dozen women, must serve a minimum of six years for the attacks in which he spiked the drinks of his victims.

Last year the Parole Board reversed a decision to release Worboys after a widespread public outcry, prompting other victims to come forward to report attacks dating back nearly two decades.

The former cab driver, who has changed his name to John Derek Radford, was jailed indefinitely in 2009 for public protection with a minimum term of eight years after being found guilty of 19 offences involving attacks on 12 women. On Tuesday, Worboys was sentenced at the Old Bailey after admitting to similar attacks on four women, the earliest in 2000.

The court heard how Worboys had since confessed to a psychologist that he plied 90 women with alcohol, drugging a quarter of them, after being inspired by pornography. Worboys admitted to psychiatrists that he had been fantasising about his crimes since 1986, motivated by a “hostility towards women”.

A probation report in August this year found: “He is potentially just as dangerous now as the point of the first sentence.”

Worboys’ confession is in line with the police’s belief that he committed 105 sexual offences against women, using his cab to pick up victims before drugging them with alcohol laced with sedatives.

In sentencing, Mrs Justice McGowan said: “I am satisfied to the required standard, on the evidence I have heard, that you are a continuing risk. I find you are currently dangerous.

“Your offending spans five years more than previously known. I do not know when, if ever, you will cease to be a risk. It will be for the Parole Board to decide in the future.”

The judge also highlighted her concern about Worboys’ ability to “manipulate others” and his “failure to admit” the risk he posed.

Worboys, from Enfield, north London, had admitted two charges of administering a drug with intent to commit rape or indecent assault, and two additional charges of administering a substance with intent to commit a sexual offence.

Prosecuting, Duncan Penny QC told the court how one victim was picked up by Worboys in 2000 or early 2001 after an evening out at a wine bar in Soho. The cab driver claimed he was celebrating a win on the horses and had previously worked as a Chippendales stripper, before pulling into a side road off the A40 and giving her red wine.

Penny said: “The last memory she had was finishing drinking the wine. She had no further memories to what took place that evening until she woke up the next day at her home address. She was naked in bed with her clothes laid out in a trail.”

Another victim, a university student in north London, was picked up with a friend by Worboys after a night out clubbing in central London in 2003. Reaching their home, the woman agreed to have a drink with Worboys but her friend left. After giving her “something fizzy”, Worboys drove to Paddington Basin where she recalled he appeared “in her face”, possibly after kissing her. She later remembered being back outside her house, lying on the floor of the cab. The following day she was “anxious” and had a “feeling of dread something bad had happened”, the court heard.

She went to the police station at the time and stood outside but ultimately decided against reporting it as she “did not know what to say”, Penny told the court. When she was pregnant years later she had flashbacks and also recognised Worboys from a picture on TV.

Mitigating, Ali Bajwa QC said Worboys had expressed “sincere” remorse. But after sentencing, Richard Scorer, a lawyer who represented 11 of Worboys’ victims, said: “Today’s sentencing will be welcome to Worboys’ many victims – but only if life really means life. Worboys is an exceptionally manipulative and dangerous individual. He will always pose a risk to women and he can never be allowed back into society.”

The Parole Board overturned its own decision to release him last November, eventually deciding he should remain in prison after noting his risk and “sense of sexual entitlement”. High court judges had ruled nine months earlier that the organisation’s decision to release Worboys should be quashed, ordering a fresh determination of the case. The Parole Board’s then-chair, Nick Hardwick, lost his job over the affair.