UDS conveyed but Built-up area conveyed is unauthorised--remedy

Sir, I have 1/4th UDS in the Land. Plot area is 6600 sq.ft. As per approved plan of 2005, the builder can construction 9600 (1.5 times). However the builder has constructed 1st 2nd 3rd floors with 11000 FSI above the permissible area. Further, be constructed the Ground and mezzanine floors with 4200 Sq.Ft to one owner and Basement floor of 2800 Sq.Ft to me for office. The construction completed in 2006. Thus he constructed 16600 sq.ft instead of 9600 sq.ft. The deviation is abnormal. He has not constructed according to their UDS. However, the property was assessed in 2006 itself by the Corporation and all other departments and all the owners are being enjoyed. Now, in 2014, the Ground floor owner filed a writ petition in the hon’ble court stating that the basement floor to be vacated and the same shall be used for generator room, lubmber room etc. as mentioned in the approved plan. Infact, we both got 1377 sq.ft in the total land. How can he built 4200 sq.ft when the permissible area is only 2065 sq.ft (1.5 times). The court direct the Corporation to decide the matter on merits. The entire building was complete during 2006, assessed by the corporation, Electricity Board, Municipality, CMDA etc. and all are residing from 2006 by paying property tax and water tax etc. Now the Ground Floor owner filed a writ in the court about the basement floor as unauthorized and needs to be vacated. In fact his ground floor and mezzanine floors are also double the permissible uds (1377 - 1.5 times = 2065) but enjoying 4200 sq.ft. The builder is still in the promotion of buildings and frequent offender in the latest buildings also. Some of their buildings were sealed by lock and key with deviations. As a owner of 1377 sq.ft of UDS (undivided share of land), what action I shall take. How to represent the Chennai Corporation and prevent by possession or how to demand my legitimate built-up area as per the approved plan from others occupation (Ground floor owner). I need fast reply sir, Thanking you