Inadequate payment of penalty for delayed possession of flat

I had booked a flat at Mahagun moderne in April 2010 and as per agreement possession was to be given by Dec 2012. Penalty was to be paid if possession was delayed beyond may 2013. Letter of completion of flat was received by me in may 2015. The builder is willing to pay the penalty charges only till Dec 2014 because as per him partial completion was applied for by him in Jan 2015 to NOIDA authority and was denied due to the pending NGT order. My plea is that the builder has been giving possession of flats for the last one year and I was not offered possession because my flat was not ready.