My HR department have refused an application for a post applied by my sister because i already work for the company and it may conflict with my job role. is this legal?
Some companies have a policy about hiring family members. They go beyond anti-nepotism rules. They are looking to avoid situations where having a close relative in the work place will cause a problem.
It can even be an attempt to make sure that they are minimizing an insider threat. Two relatives who have to double check each others work might not be as careful as the company would like. That could cost the company money if something gets missed. It also doesn't provide a second set of eyes that would serve as a deterrent to employee theft.
This is generally addressed in the employee handbook.