Many allegations had been made about Huntley before he moved to Soham
Humberside police have admitted making mistakes that led to Ian Huntley being cleared to work as a caretaker in Soham Village College.
The chief constable of the force, David Westwood, said "system failings" and elements of "human error" meant nothing had been recorded on the force's computer that pointed to Huntley's past.
Mr Westwood spoke after revealing his officers had dealt 10 times with Huntley, regarding allegations of rape, unlawful sex with underage girls and indecent assault on a 12-year-old girl. He was not convicted of any offence.
Mr Westwood said a failure to record that Huntley had changed his name was a "simple human error".
But the police chief defended the force's actions, saying other information about Huntley had not been held on their computer due to "weeding policies" that meant details of unproven cases were regularly deleted to comply with the Data Protection Act.
During tough questioning from journalists Mr Westwood said: "I am sorry that the force has weaknesses in the system. I am sorry there were individual failings."
But he later told the BBC he did not accept his force had failed Jessica Chapman and Holly Wells, rather that "the system" had failed them.
The police chief said he had spent a long time explaining the issues to Holly and Jessica's families, but refused to publicly discuss details about their conversation.
He said their procedures were a genuine attempt to comply with the letter and spirit of the Data Protection Act.
He explained that under the Act, information cannot be retained solely for the purpose of employment vetting, but can only be retained for "policing purposes".
An earlier police statement said: "It is now apparent that this made it much more difficult for us to identify individuals who were subject to unproven allegations of a similar nature over a period of years."
Mr Westwood said two separate failings had been identified.
The first was that vetting checks - such as the one made when Huntley applied for the caretaker's job at Soham Village College under the surname Nixon - were only made on the police's Criminal Intelligence Database.
The system had now been changed, he said, so that all relevant databases were checked and systems linked.
The second weakness related to the 1984 Data Protection Act.
"We had been informed by the Information Commissioner that the Data Protection Act does not allow retention of information purely for employment vetting," he said.
He said there were differing interpretations of what was required by different agencies.
Mr Westwood said: "We face here the contradictory nature of two public policies.
"First is the Data Protection Act which requires the removal of information relating to individuals.
"Secondly is the retaining of information to protect vulnerable people.
"There is no national guidance on this. It is urgently needed."
He told journalists he would support any change in the law to come from the Soham case, and welcomed the inquiry announced by the home secretary following Wednesday's murder verdicts.
Referring to human errors in the case Mr Westwood admitted it would have been "extremely helpful" if his force had been able to link the two names used by Huntley.
He said: "There was an occasion in 1999 when Huntley was interviewed by us and did indicate that he was using both names.
"We did not make a note of his alias on our records. This was a simple human error.
"Intelligence managers have been briefed on this issue to prevent this from happening again."
When Mr Westwood was asked by reporters if he felt he should resign, he replied: "It is not a matter for me".