Without mentioning names, one of my clients at work is one of the bigger police forces. I have been implementing a project with them for the last few months and I was required to go through security clearance. Which is fair enough. I had to fill out this massive questionnaire giving my details, my husbands details, my parents details and the details of my parent's subsequent partners. I had to list any criminal offences I have or have had in the past (a speeding offense with points on license). They were going to do a police record check, check the DVLA, perform a credit check.
Anyway, as mentioned in the subject title I have been informed by letter that I have been refused security clearance and they will not divulge the reasons for the refusal. I really cannot think why I would have been refused. But it now means that I can no longer work on the project and am not able to set foot on their premises. This possibly could have repercussions on my job. I can appeal but if your appeal is found to be unsuccessful they can again just tell me no and not give a reason.
It was not uncommon for an "issue" to actually be with a family member and in that case we were not allowed to divulge the reason why as the applicant may not know . Eg we had someone whose Father had falsified info on passport applications and she was declined for that reason.
Under data protection as the info did not relate to her we could not tell her the reason why.