Is there an upper limit on percentage of futures initial margin required by broker?

For the past month or so, Interactive broker has arbitrarily raised initial margin requirements on most pharma stocks. Consider the following examples:

Symbol----------------Initial margin Requirment
AJANTPHARM-------------887684
KSCL----------------------869257.5
BIOCON-------------------827490
GLENMARK----------------821450
GRANULES----------------802710
STAR----------------------748060
TORNTPHARM-------------631396
DIVISLAB-----------------554236.8
WOCKPHARMA------------517276.8

I contacted Interactive Brokers and they initially informed me that this is as per exchange requirement. So, I contacted NSE and they informed me that my broker is charging very high margin. When I contacted Interactive broker with this information, they responded that due to their internal margin policy (which cannot be disclosed), such margins have been set. Note that these margin requirements are even higher than the notional value of individual contracts.

By setting such high margin requirements, Interactive broker is effectively creating unjust hurdles for its customers to trade these contracts.

Now, I know that NSE mandates minimum margin requirement. But I cannot find any information regarding cap on margin requirement as a percentage of notional value.

Is anybody aware of such regulation on cap on margin requirement or are brokers free to charge initial margin requirements as much as they calculate as per their internal proprietary calculations?

Is there an upper limit on percentage of futures initial margin required by broker?