http://www.gmp.police.uk/content/WebAtt ... ooklet.pdf
The law is named after Clare Wood who was murdered by her violent ex partner. It allows partners, relations, friends, neighbours - just about anybody - who suspects that an individual in a relationship could be violent to check with the police and have any information disclosed.
It is obviously well-interntioned, but in its current framework [see link] it is bound to be abused for either frivolous or malicious reasons. As for the police, goodness knows where the time and manpower will come from to spend on this one law especially when it is itself abused.
The irony is that Clare's law would not have saved Clare. She got out of a violent relationship (with a person known to police for violent acts against women) only to have her ex-boyfriend cause criminal damage, harass, threaten to kill and sexually assault her. She reported him to the police on numerous occasions and even had a panic alarm fitted. Despite all of that, and even after being arrested for breaking into her home, the ex, Appleton, was let free and eventually murdered her.