Police have the power to expose paedophiles to relevant parties if they are judged to be posing a serious risk to children, but the likelihood the protection measure will be used varies significantly.
In one place where about 250 registered sex offenders reside, 61 disclosures were made last year. But in place, where there are more than 1,400 such offenders, only six notifications have been made since May 2004. The discrepancies have prompted politicians to call for the use of the powers to be reviewed.
The decision to disclose to third parties is taken on a "pressing needs test" where a particular child or adult is deemed to be under threat from a particular sex offender. Those likely to be informed, on a confidential basis, of the presence of a sex offender include headteachers, doctors, youth-club leaders, sports-club managers and landlords.
Most forces restrict disclosure to people on the sex-offenders register. But some law enforcement agencies also reveal the presence of paedophiles and others believed to be at high risk of offending who are not on the register.
Some police departments say "In doing so, we aim to minimise any threat to the community. These disclosures were made to a variety of organisations to notify those with management responsibility of employees who would potentially pose a risk."
Police across Scotland are set to introduce a formal warning system for disclosing the whereabouts of paedophiles in the spring, following a review of sex-offender legislation by Professor George Irvine. It was prompted by recent cases such as the murder of the Glasgow schoolboy Mark Cummings.
If, for example, a known paedophile moves into a house next to a school, police will have the power to warn him that if he does not move, they will inform teachers. If he ignores the warning, he will receive a final written warning. If that is also ignored, police will then inform the school of the paedophile's name and address.
Kenny MacAskill, the Scottish National Party's justice spokesman, called on police chiefs to urgently review the use of disclosure powers. "It shouldn't be a postcode lottery
... it depends on each case, but there must be clear guidelines not just for officers but for communities."
Paul Martin, the local MSP of Margaret Anne Cummings, who has campaigned for "Mark's Law", giving parents the right to know a sex offender is living in the neighbourhood, added: "Sometimes it appears more weight is being given to the rights of offenders rather than the rights of potential victims."