The controversy was caused by the disclosure that Michael Ireland - jailed for life after the 1976 "Little Red Hiding Hood" case - had been freed.
Ireland sexually abused and battered to death Susan Giles, aged 10, after accosting the girl, dressed as the nursery rhyme character, on the way to a friend's birthday party.
Her body, covered in bite marks, was found by her parents after Ireland tried to set her ablaze in a garage in Northampton.
The Prison Service yesterday confirmed that Ireland, 42, had been freed after his case was considered by a parole board panel, but would not comment on reports that he was released last October.
At his trial, Ireland admitted manslaughter on the grounds of diminished responsibility and was sentenced to life.
Sir Ivan Lawrence, chairman of the all-party home affairs committee, said yesterday that it was a "matter of concern" that someone like Ireland should be walking the streets.
Most people would feel that in the circumstances of a case like his, the killer should have to serve life, he added. But the National Association for the Care and Resettlement of Offenders, said the Parole Board would have gone through "an extremely complex and detailed process containing many safeguards" before reaching its decision to free Ireland.
The board considers reports from medical experts and the prison governor and must be sure that the criminal shows remorse and there is no danger to the public.
Helen Edwards, a NACRO spokeswoman, added: "They have to report regularly to probation and are subject to immediate recall to prison if their behaviour gives any grounds for concern."
A spokesman for the National Association of Probation Officers said the organisation had "faith" in the procedures.
Offenders who received discretionary life sentences - for manslaughter, serious sexual offence and violence - and were freed from 1983 to 1988, remained in jail on average for 10.5 years.
The average time spent in prison for discretionary lifers released in 1993 rose to 14.5 years.
The judge at Ireland's trial, Mr Justice Forbes, described the case as "the most horrible I have ever encountered" and is believed to have recommended a minimum prison term of 14 years.Reuse content