Property dispute by neighbour

There is dispute between my plot and plot behind my plot, there are two plots with same size each with 1500 sq. feet and each facing towards their respective road, On paper its 1500sq feet but actually there is extra 600 sq. feet between these two plots, we have constructed our house on 1500 sq which is on paper and using 300 sq. feet out of extra 600 sq. feet for gardening and constructed 1 wooden room in that place, Now the owner of that plot is asking us to remove that room and claiming that its his property, and when we asked him to measure his 1500 from road facing to his plot he is not ready also I asked him to make 50-50 for that also he is not ready, so intentionally he is trying to steal the extra 600 sq. feet, and he is pressurizing on me by using his power of being a police person , so I want suggestions how I can lead and take required action on him and save property.