Harassment for money extortion and breach of trust

I stay in Mumbai. My wife left my home with her mother in June 2015 by registering an NC with Police that her father is getting treatment in hospital in U.P. and my family is not allowing her to visit there. In September 16 she filed divorce in Agra on false grounds, which I am contesting. Now to trouble me her father has sent a false complaint to Mumbai Police that it was him who brought my wife back with the help of police in 2015 and my wife was a victim of DV. Surprisingly no complaint of DV or dowry was reported in NC in 2015 which is safeguarding me and everybody knows that now they are making false allegations. Police is not lodging FIR against this false complaint, saying it a family matter. Under which section should I file a case in district court of Mumbai to get an order for registering FIR and investigation. Which will help me in fighting divorce and maintenance case as I would be able to prove them with unclean hands. Should I file a suit of defamation also.