Builder taking additional money on account of VAT and keeping the same with himself for the uncertainty of future.

Q: Sir,
The Mapsko Builder for the project Mapsko Casabela, in Sector 83, Gurgaon, till 31st March 2014 had charged Vat at 1% with the surcharge of 5% which makes it to 1.05% as per the notification from Vat Authority and the payments which have been made after 31st March ,2014 till possession, they had charged Vat at 4% with the surcharge of 5% which makes it to 4.5% . Further, the builder is saying that there is no clarity on such charges from Vat Department, however, it is a mandate from the company to charge Vat at the time of Registry. Further, the Builder is saying that there is a clause in the registry that in case of any notification from Vat Authority for the increase or decrease in Vat %age.if the same has to be given to you without interest and if there is an increase in VAT amount then it has to be taken by the client.

In my scenario I had paid Rs. 1 lakh extra as I was not having any option but to say so that I can get registered my flat. But imagine there are so many flats and the money collected by the builder. He is enjoying on the money of the people.

What action can be taken in this regard.