Registration for Second car parking

Hi, I own an apartment & have self occupied the same in Bangalore, in a complex that houses 150 in all. At the time of purchase of apartment (registered in Aug 2011) I have purchased only one car park that i see allotted and stated in the sale deed along with the apartment. I now own a second car for which I require a second car parking. When I approached the builder, he mentions that there are un-allotted car parks available and the same can be allotted to me for Rs.2 lakhs. The concern is, the builder says that I will, in exchange, get a Allotment letter from the builder on the second car park and a "sale deed" or "registration" is not applicable and is also not legal. I have however heard from other colleagues that they have explicitly registered the second car park. It is my understanding that a mere letter from the builder can be challenged/disputed by other apartment owners unless it is legally registered in some form. Also, my understanding is that the BBMP controls the parking lot and allocations to some extent and how would the builder's mere letter stand valid? Please help. What is the correct process? Is my builder being honest? Meanwhile, I am also being threatened by the apartment complex to remove my second car that I have parked within my allocated parking slot (I have 2 small cars and they tightly squeeze into my single parking slot). Since mine is a corner slot with pillars on all 4 sides, it does not obstruct anyone, does not encroach into anyone else's parking slot or does not protrude out into the driveway. The apartment complex insists as the bye-law states only one car per parking, even though in my case the space can park 2 small cars. Considering that I have this conflict with the builder on the parking lot purchase, how should i address the threats from the apartment association? Please help