Profession tax of employee of contractor

ABC Pvt Ltd is a private limited company engaged in the business of manufacturing of Iron & Steel and the major processing works are handled by contractor .Please guide me who is liable to deduct profession tax from labour of contractor ( ABC Pvt Ltd or Contractor ).In my opinion it is the responsibility of contractor to deduct and pay profession tax of HIS employees.There is no Employer-Employee relation between ABC Pvt Ltd and labour of Contractor.Please guide.