As mention in Gour Govind Maharajs Book – Suddha Nama Bhajana
This Hare Krsna maha-mantra, consisting of sixteen-names and thirty-two syllables, is available in all the Vedas. The Kali-santarana Upanisad is one of the Vedas and such concocted slogans are not available in the Vedas. One should not follow these rascals and chant these concocted names. This is most important and one should understand that in every yuga there is a taraka-brahma-nama; and
In the Kali yuga the taraka-brahma-nama is:
hare



