Please Help: Service Tax on Book Maker Service

I would be thankful if someone can let me know whether the amount received from the Punters (Horse Racing) is liable to service tax?
The Book Makers receive a percentage of amount in addition to the betting amount from the punters. As we already know that betting is under the negative list, the betting amount is not liable to service tax, but how about the additional amount that the Book Makers receive in addition to the betting amount? Whether this also comes under the negative list or is it liable to service tax?