The key thing is 'purpose'.
Is the request for private data fit for purpose? If the answer is yes, then the request for consent is in order.
With regard to employment, I want to believe the prospective employer has a right to check out your background. That's why CVs used to ask for 3 Referees (not sure if they still do ;-)
Additionally, depending on the sensitivity of the post, you will be asked for CID Clearance, Credit Check, Anti-Corruption Reports, Tax Returns, Birth Cert, ID na kadhalika.
If its a supermarket or a hospital or university asking for this data, you can sue them and win.
But if its a prospective employer asking for this private data and you sue them, you are unlikely to win the case since their right to do due diligence to protect the company from hiring suspicious employees supersedes your right to hide your data.
+ you retain your right NOT to apply if you feel the data request is an overkill.
walu.