No redevelopment by builders for 1.5 years, what action can I take?

Hi, There is a building in Malad west, Mumbai with 7 tenants which was demolished 4 years back doing setting with BMC by one of the member of society ( having political connections ) saying he will do redevelopment and all members agreed signed up irrevocable consent. Post that for 1-1.5 year nothing was done. 4 other members realized that they need to do society registration and deemed conveyance as builder is doing nothing to safeguard the property and got it done somehow with their own expenses. Now, builder being one member ( also chairman ) in society along with 2 other member ( who had some mutual extra area temptation ) are with builder and its 4 years now. There is majority ratio of 4:3 in society, the builder ( chairman ) who has keys of demolished plot say he is developing and doesn't allow any other builder to develop. On the other side he doesn't take any step as well. Pls help Thanks in Advance