The mother of murdered toddler James Bulger accused authorities of covering up the extent of his killer's "vile" behaviour as he was locked up once again.
Jon Venables has been living anonymously since his release from a life sentence for the kidnap, torture and murder of two-year-old James 25 years ago.
But in November last year he was caught with a stash of indecent pictures of children on his computer for a second time.
During a hearing at the Old Bailey, he pleaded guilty to downloading 1,170 images from the dark web over the course of several months as well as having a "sickening" paedophile manual.
Mr Justice Edis jailed him for three years and four months but said the Parole Board will decide when he should be released back into the community.
He said the latest images were "vile" and "heartbreaking", adding that many showed abuse of young boys like James.
Mr Justice Edis told Venables: "This case is unique because when you were 10 years old you took part in the brutal murder and torture of James Bulger.
"That was a crime which revolted the nation and which continues to do so even after the 25 years that has passed since it happened."
Of the images he downloaded, the judge said it would be "heartbreaking for any ordinary person to see this kind of material".
The judge described the manual as a "vile document" and told Venables that by consuming these "products of barbarous evil", he caused abuse to happen.
James's mother, Denise Fergus, and father, Ralph Bulger, were in court for the hearing.
Afterwards, a spokesman for Mrs Fergus called for an inquiry and accused authorities of "colluding" to cover up Venables' pattern of vile behaviour.
The court heard that he breached his parole in 2015 by accessing the internet but was only handed a police caution rather than being brought back to court.
The spokesman said: "There should be no further collusion or attempts to cover up his offending behaviour. If re-bailed he must be kept on a very tight leash."
He said the sentence was "too short" and Venables would leave court "believing he got away with it".
Earlier, the judge declined a request to delay sentencing so Mr Bulger could make a victim impact statement, saying: "I know the impact on these two people of what happened when their child was killed.
"I know already how it must be for them when that tragic event is once more brought into the public domain into court and so on because of the offending of one of the killers."
James was kidnapped, tortured and killed by Venables and Robert Thompson, who was also 10, in February 1993.
Venables, who has lifelong anonymity, was released on licence in 2001 after serving eight years for murdering James.
In 2010, Venables pleaded guilty to charges of downloading and distributing child pornography and was jailed for two years, although he was not released until 2013.
That was not the only time he had breached the terms of his licence.
In September 2008, he was arrested on suspicion of affray after a drunken brawl and was given a formal warning by the Probation Service.
Later the same year, he was cautioned for possession of cocaine after he was found with a small amount of the class A drug.
Appearing on court via video-link from custody, he pleaded guilty to making 392 category A images, 148 category B images and 630 category C images.
He also admitted having the paedophile manual on or before November 17 last year.
Prosecutor Louis Mably QC said that, when Venables' computer was seized, police found images of children mainly aged between six and 13, although some were younger.
Mr Mably said the manual was "a disgusting and sickening document which falls far below any recognisable standard of morality".
He said Venables had software on his computer to browse the dark web.
As he was being taken to a police station, Venables said: "This is my own fault. I have let people down again.
"I have had stupid urges, inquisitive. I'm not going to be seeing this for a lot of years.
"It's not going to be a slap on the wrist for me."
The court heard that a report had found that Venables was a "high risk of real harm to children".
It stated that he has a "long-term and profound interest in children".
Mitigating, Edward Fitzgerald QC said Venables had "expressed profound remorse for his part in the murder (of James) and worked hard for rehabilitation".
He said he never attempted to contact children for sexual purposes and the images he downloaded were for his own personal use.
When he was arrested, he expressed "dismay" and remorse and said he needed help to understand why he did it.