Dispute with the builder

Hello All, My father, selected a builder in our locality for reconstruction of our home. Builder did not get into any signed agreement stating to settle things later. His main aim was to duck his tax and safety responsibilities arising because of the construction of our home. Builder did very very shoddy work and we are still facing numerous seepage and other problems. We even got the terrace flooring relaid again at our own cost to prevent the leakage/seepage. We are still doing repairs at our own cost. He never did anything for us since we entered our house in April 2019. Situation now is, we are in the house.. He (in-spite of communicating himself) sent many people (including local property dealers and others neighbors) for his settlement. We persistently asked all to tell him to come to us but he never showed up. Now, one of his associates, have filed a writ petition in high court against our house stating that it is built illegally and should be demolished. Almost all the houses built the way our home is built. In fact the house builder has built for himself (and 2-3 nearby buildings) are 6 story high (as per rules 5 stories are allowed - Parking + 4 floors within 15 meters). (info based on best of my knowledge). What shall be our course of action. Is Tax Evasion Petition one of the way? Please advise.