Victims of black-cab rapist John Worboys were "shocked and distressed" to learn of his release in the media, a government-backed review has found.
The government ordered an urgent review after widespread outcry over the Parole Board's decision to release the serial rapist from prison and the manner in which victims were informed.
Dame Glenys Stacey's report found many victims were left "shocked and distressed" to see the decision in news headlines.
When they were directly contacted, their names and addresses were spelt wrong in letters.
These mistakes suggested "a lack of care or concern", Dame Glenys said.
"Those women not in contact with the scheme - the majority - learnt of the decision through the media. All who spoke to us described their shock and distress," she added.
"They had not felt prepared for this outcome."
The findings were released as Worboys appeared in person at the High Court to hear whether the decision to release him will face a legal challenge.
Separately, members of the Parole Board are appearing before the Justice Select Committee to explain the decision to release Worboys.
Worboys was jailed indefinitely in 2009, with a minimum term of eight years, for drugging and sexually assaulting women passengers.
The chairman of the Parole Board, Professor Nick Hardwick, has called for the reasons for a prisoner's early release to be made public to help with transparency.
Professor Hardwick said: "One of the things we should look at is victims, who want to get one, getting a summary of the parole board's decisions. I certainly think they should know more about licence conditions.
"The presumption should be that we tell victims as much as we can."He added: "It should be possible to provide some statements publicly about the reasons for a decision."
The Parole Board chief favours publishing an online register of cases so that any member of the public can track developments.
Justice Secretary David Gauke has ordered a review of the transparency of the board's decisions and said planned changes could be laid out by Easter