More than 700 paedophiles have been identified since the introduction of "Sarah's Law" in 2011, Freedom of Information requests have revealed.
Nearly 5,000 requests for information were made in England, Scotland and Wales; one in seven resulted in a paedophile being revealed.
The disclosure scheme was named after eight-year-old victim Sarah Payne.
It means a parent or guardian can ask police if a person who has contact with children is a child sex offender.
"There must be sufficient access to or connection with the child by the subject to pose a real risk of harm and therefore justify disclosure," say the rules governing the scheme.
Some 4,754 applications have been made since the system was introduced two-and-a-half years ago but the number is falling. There were 1,944 in 2011-12 and 1,106 so far in 2013-14, while disclosures were 281 in the first year and 122 in current year to April.
Child safety campaigners said they were concerned that the disclosure rate was too low, suggesting that many offenders were not on police records.
In England and Wales, Avon and Somerset Police revealed the highest number of paedophiles at 42. This was followed by followed by 39 in Devon and Cornwall, 36 in Thames Valley and 33 in Norfolk. The identities of 49 child sex offenders were released by police forces in Scotland.
Donald Findlater, director of research and development at child protection charity the Lucy Faithfull Foundation, said: "Given the apparent drop in applications since the start of the scheme, albeit small, we have some concern that people may not know the scheme is available to them.
"We would like to see continued public awareness and publicity, whether by local forces or nationally by the Home Office, so that people know that this means of checking someone out exists."
The scheme was introduced following the campaigning of Sara Payne, the mother of Sarah. Her daughter was was found in a field near Pulborough, West Sussex, after she was killed by Roy Whiting in July 2000.
Under Sarah's Law, police will reveal details confidentially if they think it is in the child's interests.
Christopher Stacey, director of services at offender reform charity Unlock, said: "It is important to strike the right balance between the need to protect the public and enabling people who have served their sentence and rehabilitated themselves to move on positively with their lives.
"There already exists a detailed framework in place which is designed to enable the police, probation services and other agencies to share information with members of the public where there is a safeguarding concern.
"As a result, it is unclear what value this scheme is adding, with serious questions about the statistics being used to defend the effectiveness of the scheme."
Jon Brown, NSPCC lead for tackling sexual abuse, said there was a delicate balancing act.
"Sarah's Law is not a silver bullet to end child abuse, and giving the public information about where sex offenders live is just one part of the jigsaw," he said.
"Informing the public of their whereabouts has to be done properly, professionally and judged on a case-by-case basis.
"Forcing a child abuser underground because of a fear of vigilante attacks won't make children safer as the authorities will lose track of them."
The figures were up to November this year. The disclosure scheme does not apply in Northern Ireland.