Their names will be added to the computerised database at the rate of about 3,500-a-year - including about 1,000 subject to the provisions of the Mental Health Act.
The register, being set up under the Sex Offenders Act, is intended to enable police to keep track of known sex offenders as they move around the country. But its scope will be limited and a United States-style "Megan's Law", under which the whereabouts of offenders are widely publicised, is ruled out for fear of vigilante action.
From 1 September, offenders convicted of or cautioned for a range of sexual crimes will have to register their addresses in the National Sex Offenders Register proposed by the previous government, and tell the police when they change their name or move home.
Guidelines published yesterday on police use of the information make it clear that ministers are opposed to forces automatically giving local residents the names and addresses of convicted offenders who move into their area on release from prison. Instead, forces will be expected individually to assess the seriousness of the risk posed by offenders, and whether naming them will displace offending somewhere else or drive offenders "underground" where they cannot be monitored by local agencies.
Alun Michael, the Home Office minister, said: "I believe the guidelines strike the right balance between keeping a check on where sex offenders, in particular paedophiles, are living, while at the same time allowing them the chance to mend their ways in the community."
But the guidelines have their limitations and are likely to be followed up with new measures for post-release supervision in the Government's planned Crime and Disorder Bill in the autumn. The Bill is expected to provide for supervision of sex offenders by probation officers for up to 10 years.
Harry Fletcher, assistant general secretary of the National Association of Probation Officers, said: "It will take 10 years for the register to be up and running properly. The real issue is the degree of treatment and control."
Under the measures announced yesterday, police will be able to pass on details to employers, voluntary organisations and members of the public. The guidance states, however, that "disclosure to a member of the general public will very much be the exception to the rule". Information would usually be restricted to a local education authority, or individuals like a headteacher or playgroup leader.