Not getting occupancy certificate & completion letter from Builde

Hi, We purchased new flat in 2012 and also shifted to new place without getting OC and completion letter from builder as builder had no objection to it and he had comited us to provide OC within 1 year. Its 2016 and we are still without OC. Building have only 10 apartnments in it out of which 8 apartments are sold to individual like us. 2 apartment are still with builder and he is not seeling it to anyone. Also he is not providing OC and neither ready to take any meetings. All cost like Property tax, Electricity bill, Watchmens salary, Water bill are paid by Builder only. We 8 flat owners are not happy with it and we want to get OC as soon as poosible and want to form register society. Can you please suggest what we can do to get the OC from builder? Builder is very much known in one of the political party. We 8 flat owners are ready to take possible action against him. can we send him legal notice as he is not available for meeting at his office or in building? Please suggest how we can get OC from the Builder?