Police and social services were alerted to Ian Huntley's relationships with several young girls but no action was ever taken against him, the Bichard inquiry heard today.
Huntley was accused of having sex with four girls under the age of 16, one of them aged 13, during 1995 and 1996.
Social workers, parents and even a deputy head teacher all raised concerns about Huntley's behaviour, but no criminal charges were ever pursued.
One officer, Detective Inspector Peter Billam, who is now retired, was involved in Humberside Police's handling of three of the four cases, the inquiry was told.
The first allegation came to light when the parents of a 15-year-old girl, referred to as A B, complained in June 1995 that Huntley had had unlawful sexual intercourse with their daughter.
It was later alleged that A B and her younger brother had moved out of the family home and were staying with Huntley.
When he was interviewed by police Huntley said he knew the girl was 15 but did not think it was an offence to have sex with her as he believed they had her parents' consent.
Huntley was then told by police it was an offence to have sex with a girl under the age of 16, the inquiry heard but ultimately no action was taken against him.