False FIR by a girl against my father for sexual harassment

My father has been trapped under a false complaint by a girl in his office. She has no proofs against him but some people in his office are supporting that girl because they don't have good relations with my father. some of the people in his office are supporting my father too.police has registered FIR U/S 354A , 509 against him without any proof. Police is constantly harassing my father( ill mannered language ).He is working as senior accounts manager in a good company. There is one more person (company's senior manager) who is trapped in this matter. The girl trapped the manager by speaking to him lovingly and inducing him to do some intimate act (touching), she recorded that( but still has not shown it to anyone, so we don't know whether its correct or not). But my father(accounts manager) is not involved in this even 1%. But since he was senior manager's good friend he was trapped in this too ( but she does not have any proof against him , since he did not do anything). Now police is constantly harassing my father to come to the police station. What should we do to get the preventive bail? Will he definitely get a bail? How should we avoid being called by the police again and again? Should we file an FIR with the police against that wrong FIR and when? How can my father prove his innocence? How can he file case against that girl to get her jailed? How can he prevent himself from being caught in another false FIR from that girl? some of the office people are not supporting my father, they are interested in suspending him from office due to some jealous reasons, without any proof, how can he avoid that through legal remedy?