The management of sex offenders requires "considerable improvement" to ensure members of the public are not put at risk, a new report warns.
A joint study by the probation and constabulary inspectorates calls for police and probation officers to better monitor these offenders.
It also criticises management of cases as "poorly coordinated and inconsistent", and finds gaps in training of relevant police and probation staff in risk assessment processes.
As such, it recommends that only properly-trained specialist officers be given responsibility for managing sex offenders in the community, and that these officers receive "dedicated proactive supervision".
"This inspection makes clear that the oversight of high and very high risk of harm cases by police officers and probation staff needs to be improved," said chief inspector of constabulary Ronnie Flanagan.
"It is vital that police officers who are managing sex offenders in the community are appropriately trained and receive regular supervision. This is challenging and important work and demands a high degree of professionalism."
The Association of Police Chief Officers (Acpo) welcomed the report, and said it was aware that sex offender management should be dealt with by properly trained staff.
A public protection manual was currently being drawn up to form the basis of a new training scheme for staff and supervisors, it said, expected to be introduced in 2007.
Many of the concerns raised in today's report relate to visits made to the homes of sex offenders. It says staff do not always produce accurate records of their activities, and there is a "lack of clarity" about the purpose and frequency of these visits.
"Competing demands" on police time, such as the threat of terrorism, were also blamed for the inability to provide comprehensive surveillance of sex offenders.
However, the report does admit that there have been some positive steps in the management of sex offenders.
The Home Office has defended the current system by insisting that the multi-agency public protection arrangements are proving successful, but have only been up and running for five years.
There are almost 29,000 convicted offenders listed on the sex offenders' register, of which 626 are viewed as high risk and 547 are regarded as violent offenders who pose a risk to local communities and need a high level of surveillance.