Srila Bhaktisiddhanta Saraswati Thakura
Rajen Babu: Isn’t the kanistha-adhikari qualified to give initiation into the mantra?
Srila Bhaktisiddhanta Sarasvati: Where is the kanishtha-adhikari coming from? Who gave him the adhikara? A kanishtha-adhikari can never become a guru.
Rajen Babu: Can a madhyama-adhikari give diksa?
Srila Bhaktisiddhanta Sarasvati: HE CAN ONLY PERFORM THE INITIAL DUTIES OF DIKSA. It is the uttama-adhikari maha-bhagavata Vaisnava who is actually the diksa-guru. There are two types of Vaisnavas – the ragatmika and the raganuga. Those who are from the eternal realm offer service to Sri Krsna directly. These ragatmikas serve Sri Varshabhanavi and Her direct expansions. Those who perform direct service to the ragatmikas and take shelter in them through the performance of smarana are raganugas. These are spiritual gurus.
Quoted from August 8th 1934, Srila Bhaktisiddhanta Sarasvati Q&A with Sriyukta Rajendranath Pal Chaudhuri Mahasaya, the famous Zamindar of Louhajang.