Cheating by PWD Construction Contractor

My father is a private contractor, he got a job from a registered PWD contractor (contractor ID - 169562012) for construction of a road ,which my father did completely and perfectly. But in order to complete the construction he had borrowed money from market since the contractor said that the bill has not passed and he had no money. Now the contractor is refusing to pay the money for the work which my father completed. On enquiry we learned that the bill for the road had already passed and he got paid for the road construction from the govt. ,but he is refusing to pay the money which he owed us. We complained to the police but they are not initiating any legal actions since he has some political power. Even his brother verbally abused my father on broad daylight to scare us to not ask for money. He also has some illegal factories and illegal properties beside the national highway and many more. So what should we do since the money my father borrowed has to be returned with interest and the PWD contractor is stalling us.Please Help.