SARAH’S Law has seen 21 paedophiles unmasked in the West Mercia Police area since the launch of the scheme – aimed at protecting children from sex offenders.

The West Mercia force was one of the first constabularies to adopt the Child Sex Offender Disclosure Scheme, known as Sarah’s Law, as a pilot in August 2010.

The disclosure scheme was named after eight-year-old victim Sarah Payne and means concerned parents or guardians can ask if anyone who has contact with children is a sex offender.

West Mercia Police has since received 131 formal applications for information, with a total of 21 paedophiles being identified.

Glouceshire Constabulary adopted the scheme in the following year. Since then, there have been 67 applications, leading to nine disclosures.

Nationally, there have been 708 disclosures from a total 4,754 applications – meaning about one in seven requests results in a child sex offender being revealed.

Child safety campaigners have voiced concern that the disclosure rate is too low and that the number of requests being made is falling. Formal applications have fallen from 1,944 in 2011/2012, to just 1,106 so far in 2013/14.

Donald Findlater, director of research and development at Lucy Faithfull Foundation, a charity which works with sexual abusers as well as victims, 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.”

However numbers have remained more consistent in West Mercia, with 51 applications in 2011/2012 and 40 so far in 2013/14.

Under Sarah’s Law, police will reveal details confidentially if they think it is in the child's interests.

But Jon Brown, NSPCC lead for tackling sexual abuse, said disclosing information is a “delicate balancing act”.

“Informing the public of their whereabouts has to be done properly, professionally and judged on a case by case basis,” he said. “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.

“Ultimately, the route we must pursue must be guided by what we know keeps children safe, which is a co-ordinated approach including deterrence, treatment and advice and information to the public.”