illegal aggrements and collateral transactions.

i have my own co-operatve society in maharashtra.our former secretery had purchased a room of 170sq ft in MHADA scheme,by an agreement we had already paid him full amount,but he did not produce us a noc for registry.

Actually , that agreement was been made in 1997 on 20 RS  stamp paper.but unfortunatrely we did not notary or registered that agreement.and now when we approach him he said he will never registered us that room.but the possession of that room is still under are organisation.so pls kindly suggest me what should i do in this case.

its urgent