Illegal encroachment on public land

My father was managing a business in the above mentioned premises. He was one of the oldest, setting up his establishment and was also President of the Association. In this area there are quite a few public land patches and several miscreants were after it (wanted illegal occupation). But, only because of my father they were not able to do it. Unfortunately, my father passed away in March 2005. As you can guess, the miscreants started to occupy the public land. And so far they have occupied some land and have managed to build only ground floor and could not proceed as I wrote to the local municipal authorities/DDA etc. One of the occupants is a politically connected person from the party in power. I want to file a PIL and get the unauthorized property demolished and the wrong doers punished. I am aware that the local MCD officials, Police, electricity department officials are involved. Maybe that  piece of vacant land could be used as a green park instead of wealth for these miscreants.