Probation staff were warned serial rapist Joseph McCann posed a risk of sexual offending and could have recalled him to jail, a report says.
McCann was given 33 life sentences after being convicted of a series of offences against 11 women and children.
There were eight opportunities to recall McCann to jail before he went on a spree of sex offences last year, the Serious Further Offences report found.
Justice Secretary Robert Buckland promised an independent review.
A summary of the report said McCann should have been kept in jail at least until the Parole Board was satisfied it was safe to let him out.
It says there were eight occasions when this process – called “recall” – was considered.
“The most significant practice failure was the repeated failure to recall Joseph McCann or to reflect critically on earlier decisions not to recall him, in the face of both court and prison staff communicating their concerns,” the report said.
It disclosed that in 2011, when McCann was in prison for burglary, police shared information dating back to 2003 and suggesting McCann “might pose a risk of sexual harm and exploitation to teenage girls”.
The report added: “It appears that the pressure on the staff throughout 2018 and the chaotic transfer of the case between numerous offender managers also significantly impacted their ability to comprehensively review McCann’s historical record, and therefore to identify the previous references to sexual violence.
“Had offender managers reviewed the historical records, including the police intelligence, they might have instigated one to one work with McCann to address sexual violence.
“However, aside from this historical intelligence from 2003 and the letters intercepted by the prison in 2009, there were no more recent indicators of concerning sexual behaviour, and this failure should be viewed in this context.”
The prison holding McCann had also intercepted two sets of letters from McCann with “disturbing contents” which “indicated he posed a risk of sexual harm”.
McCann was released in March 2017 under strict bail conditions, but jailed again later that year.
He was released at the halfway point of his sentence in February 2019, two months before he went on a sex offending spree in Watford, London, Greater Manchester and Cheshire.
Alan Collins, a lawyer for McCann’s victims, said the report made for “hard and distressing reading”.
“It is unforgivable that the probation service, for unfathomable reasons, put McCann’s perceived interests before the safety of the general public,” he said.
“McCann posed a real risk to the public and the systems in place to manage the risk he posed were corrupted through ineffectual management and poor judgment.
“As a direct consequence, he was let loose on an unsuspecting public with terrible consequences.
“Lives have been damaged, if not ruined, as a result of what happened and the Ministry of Justice must accept full responsibility and… accept that it has to be accountable for McCann and the crimes that he committed when he should have been in prison.”
The Ministry of Justice, which carried out the review, said the chief inspector of probation Justin Russell will be asked to carry out an independent review of the National Probation Service’s management of McCann and how the process of recalling offenders to prison is working.
The Attorney General also said he has referred McCann’s sentence to the Court of Appeal under the Unduly Lenient Sentence scheme. A hearing will take place on 25 March.
In December, describing McCann as a “classic psychopath” the sentencing judge said his campaign of abduction and sexual abuse was unprecedented.
The judge called for an investigation into failings in the probation system which had left McCann on the streets.