Police have played down fears that allowing parents to check if someone with access to their children is a sex offender may cause vigilante attacks.
The scheme known as "Sarah's Law" was proposed after the murder of eight-year-old Sarah Payne 10 years ago.
The Home Office pilot scheme is now being extended to eight more forces.
Chief Constable Paul West of the Association of Chief Police Officers said it was "realistic" to think people would keep information to themselves.
The scheme was piloted in four areas in England from September 2008 and will be expanded to the whole of England and Wales by spring.
Sarah was kidnapped and murdered by a convicted sex offender, Roy Whiting, in West Sussex in 2000.
BBC News
