Council staff, charity workers and doctors could be required by law to tip off police about anyone they believe could commit a violent crime.
The Home Office proposals, leaked to the Times newspaper, insist public bodies have "valuable information" that could identify potential offenders.
Possible warning signs could include heavy drinking, mental health problems or a violent family background.
The Tories say the plans would require staff to "snoop on their customers".
Civil liberties campaigners are concerned that people could be put under police surveillance despite having committed no crime.
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The proposals for "multi-agency information sharing" were circulated in Whitehall by Simon King, head of the Home Office violent crime unit.
They are being viewed as an attempt to close a loophole which allowed Soham murderer Ian Huntley to get a job in a school, despite previous accusations of violence.
'Worrying profile'
The leaked document states: "Public bodies will have access to valuable information about people at risk of becoming either perpetrators or victims of serious violence."
It says when staff become "sufficiently concerned" about an individual, that person should be should "risk assessed" and, if necessary, referred for further attention.
Mr King suggests two new agencies be created - one to collate reports on potential offenders, the other on potential victims.
"How far are we willing to go in pursuit of the unrealistic promise of a risk-free society?"
New laws would also be needed to place staff under a statutory obligation to report any concerns, he adds.
Supporters say the plans build on existing local arrangements used to try to prevent domestic violence by identifying those at risk.
But Jago Russell, policy officer at campaign group Liberty, said the proposals left many "unanswered questions" about what should be done about someone with a "worrying profile".
"How far are we willing to go in pursuit of the unrealistic promise of a risk-free society?"
The Conservatives claim the policy would simply increase bureaucracy.
Shadow Home Secretary David Davis said police already had a considerable "administrative burden" without having to "wade through file after file of speculation and guess work".
A spokesman for the Home Office said the proposals were at an early stage and no decision had been made.
"However, the Home Office has its duty of public protection as its top priority," he added.
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