Purchase of property on pagdi system.

My father purchased a property on pagdi system in 1983, 10 years later previous landlord sold the property to the new landlord. Since then the new landlord does not accept rent and has been harassing us. He will not let us carry out any repairs too. What is the law regarding repair works? This being a ground floor house it had an existing extension when we purchased it, the landlord claims it to be illegal too, what is the law for this? he does not have any evidence apart from the map no pictures etc of vacant area. Kindly advice.