A known paedophile was able to repeatedly rape a nine-year-old girl despite being under community supervision.

Kevin Hazelwood, from Brighton, who police described as "evil", was already on the sex offenders' register for accessing internet child pornography but was still free to subject the girl to a string of sexual assaults.

Sussex Police said while local authorities did "everything" possible to supervise sex offenders, "human rights" had to be balanced against risks posed by individuals.

Hazelwood's conviction, however, has prompted calls for a overhaul of the child protection system.

He pleaded guilty at Lewes Crown Court to six counts of rape, two counts of attempted rape and two of indecent assault, on the same victim.

The 40-year-old, of Oriental Place, Brighton, has also admitted charges of sexual activity with or in the presence of a child under 13, and is due to be sentenced on April 20.

The latest conviction of a pervert, who was already known to have a sick attraction to children, comes a day after The Argus exclusively revealed Brighton and Hove social services employed a social worker years after concerns were raised about his behaviour towards youngsters.

Gordon Oliver, who went on to commit a string of sex attacks on children, was employed in a senior position in Brighton social services until 2004, two years after colleagues warned bosses they were worried about attention he paid teenagers in his care.

He was convicted of abusing five children, including a Brighton boy he groped during swimming sessions after being allowed to return to work with nothing more than an advisory warning telling him to avoid close contact with children.

Oliver, 58, who lived in Washington Street, Brighton, is now serving five years in prison.

A grandmother told The Argus on Thursday how Oliver had ruined her grandson's life and yesterday she was left disgusted by the latest revelations about Hazelwood.

She said: "The system is just letting kids down constantly. Somebody should be held accountable for this."

Sussex Police said Hazelwood would also be sentenced in April for historic indecent assaults on a girl dating back to the early Eighties and for possessing indecent movies of children.

Detective Superintendent Russ Whitfield said a "full review" of Hazelwood's case would be carried out.

However, he said it was not possible for local authorities to "eliminate" the risk of known sex offenders committing more crimes. Risks posed by sex offenders in England and Wales are monitored under Multi-Agency Public Protection Arrangements (MAPPA).

This involves bodies such as the police, probation officers and prison staff working to "manage people who pose a serious risk of harm to others".

Mr Whitfield said: "We do absolutely everything we can to manage sex offenders in Sussex. We legally have to balance a person's human rights versus the risk they pose to society.

"The MAPPA can only manage and reduce the risk. It cannot eliminate the risk."

Mr Whitfield said supervising an offender as "deceitful and manipulative" as Hazelwood was "obviously very difficult".

He said: "He developed relationships with adults, which he did not disclose, and used these relationships to target children.

"Brighton and Hove Local Children's Safeguarding Board will conduct a full review to see if there are lessons to be learnt from this case. Our thoughts are with the victims and their relations. I pay tribute to the officers who investigated this horrible crime."

Derek Green, director of clinical services for globally renowned sex crimes agency RWA which works with paedophiles and assists the police and the probation service, said: "The sexual offenders register is an over-rated instrument.

"You have to report your address to the police once a year, you have to report any change of name or if you change your job to one that may be with children. You have to inform if there is a short change of address. That's about it."

He said more use should be made of sexual offender orders, which can ban paedophiles from going near schools or parks, entering a geographical area such as a town and from associating with anyone under the age of 18. Breaking an order is a criminal offence.

MAPPA began operating in April 2001 and assesses the risks posed by offenders in every community in England and Wales. Advice is sought from organisations such as social services, local authority housing, health services and youth offending teams.

A spokesman for the Sussex Probation Area said its review had found Hazelwood had been assessed and managed in accordance with national standards.

He said: "Public protection is our top priority but it is never possible to entirely eliminate risk in these cases."

A spokeswoman for children's protection charity the NSPCC said the latest MAPPA reports showed only the most dangerous sex offenders, who account for one in 20 of all known offenders, were fully supervised in the community.

The charity wants MAPPAs given more resources so current arrangements for high risk offenders could be extended to all medium risk offenders.

Director of public policy at the NSPCC, Phillip Noyes, said: "Close supervision means the police and probation services can move in if a freed prisoner approaches children. By acting early we can prevent an offender committing yet more heinous crimes of abuse."