Illegal construction close to my boundaries

My neighbour bought a house from a promoter but the one bathroom is close to my boundaries nearly 8 years ago it was build it is soo close that there is no place and we built our property boundary 20 years ago when we bought this property we asked the promoter not to built the bathroom without leaving a little place and close to our boundaries but he didn't listen to us that time my area was under panchayat so we couldn't take much step because we didn't know how to stop it against promoter and we also asked the buyer who is actually the owner of that house for not to buying that or break that part cause that could be a issue in future but they also didn't listen to us now I want that further building shouldn't be constructed above the illegal portion which is closely attached to my boundaries and under the roof of their total house. If they build the 1st floor it will be so close that we can touch each other's walls in that portion that may lead to more issues in future. so how can I stop to do this is it possible? Please help me into this matter.