Social workers and doctors working with potentially dangerous people should be ordered to share information a police chiefs' organisation has said.
The statement comes as a new report into killer Michael Stone found facts about his mental health were not passed between agencies.
Brian Moore of the Association of Chief Police Officers (ACPO) told the BBC avoidable tragedies could continue to happen unless regulations were changed and insisted "too much importance" is placed on patient confidentiality.
Mr Moore, deputy chief constable of Surrey Police, told the BBC: "There is no doubt that in the past there have some violent deaths and serious assaults that may have been prevented if public authorities such as the police, social services and health had shared information about the risk posed by individuals who have come to their attention or been in their care.
"However, despite numerous public inquiries and recommendations, there is still incoherence and ineffectiveness in the way agencies share information about risk."
Some professional cultures placing the duty to maintain confidentiality higher than the duty to protect from violence, Mr Moore explained.
"The overall picture is one of uncertainty, lack of clarity and, a lower standard of risk assessment than the public have the right to expect," he said.
"Many protocols, advice and guidance have been developed over the years, and although well-intentioned, they lack effectiveness and accountability."
This week's report into the care and treatment of Michael Stone stopped short of saying the 1996 murders of Lin and six year-old Megan Russell in Kent could have been prevented.
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But it revealed a picture of agencies not communicating with each other, of records being lost and of warnings not being acted upon.
