A similar question has been answered on Tilak Marg with regard to RTI application seeking third party information: Refusal of RTI information held in fiduciary capacity or supplied by third party and treated confidential. It mostly covers your question also.
You can try to file appeal against refusal to provide RTI information. There is a provision for the second appeal also, and thereafter going to high court against refusal of information.
Another option could be to file complaint with the appointing authority (or his higher authority if the appointing authority is complicit in the wrong appointment) about the fake caste certificate used and such authority can then conduct an enquiry and take action if the allegation is found to be true.
Yet another option could perhaps be to approach the court (more so, if you have been denied the appointment due to the selection of the person with fake caste certificate), but then you’ll need to give some basic evidence in respect of your allegations.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.