Smear: NKT ordination is not valid
Truth: Because the system of ordination in the NKT follows Buddha Shakyamuni’s teachings on ordination interpreted by Geshe Potowa (1031-1106), and this contains the essential meaning of all ordination, it is entirely valid.
It is important to understand the essential meaning of ordination before judging whether NKT ordination is valid or not. Just because it is different from the Tibetan tradition doesn't make it invalid.
At the present time the NKT-IKBU has about 700 ordained people around the world. The way of granting ordination was designed by Geshe Kelsang following the ancient Kadampa tradition. It is very simple and very practical.
The definition of ordination vow is a special moral discipline motivated by renunciation and received by means of a ritual practice given by an Ordaining Preceptor. This is true for all traditions of ordination in Buddhism. The aspect of the ordination may change in accordance with the conventions of society but, for as long as the essential meaning of ordination is maintained, it is entirely valid.
The real meaning of ordination is to develop the mind of renunciation (the wish for liberation from samsara's suffering) and then to practice the actual method for attaining liberation, which is called “the three higher trainings” – the practices of higher moral discipline, higher concentration and higher wisdom, until liberation or nirvana is achieved.
Traditionally, Tibetan Buddhism follows the Vinaya Sutra, which comes from the Hinayana tradition. In the system of Tibetan Buddhism, the level of ordination is determined by the number of vows. Someone is a fully ordained monk if they hold 253 vows, or a fully ordained nun if they hold 364 vows. (There is no longer any tradition for full ordination for women in the Tibetan tradition and so Tibetan Buddhist nuns are secondary to monks.)
The NKT ordination follows the tradition of ordination explained by Geshe Potowa and other Kadampa Geshes. According to this system, it is the level of renunciation that determines the level of ordination, not how many vows you hold. In NKT ordination, a monk or a nun becomes 'fully ordained' (Gelong or Bhikshu (monk), Gelongma or Bhikshuni (nun)) by holding the ten vows of ordination and having developed the realization of renunciation, that is, having developed the spontaneous wish for liberation such that it is ever-present in the mind, day and night.
The essence of the ten ordination vows of a Kadampa monk or nun is the condensation of all the vows of a fully ordained monk or nun contained in the Vinaya Sutra. The ten ordination vows are derived from a different teaching of Buddha, a Mahayana Sutra called The Perfection of Wisdom Sutra. The vows are very practical, compatible with the norms of Western society and can easily be integrated into daily spiritual practice. Moreover, monks and nuns are equal; there is no discrimination against nuns.
For more information on ordination in the New Kadampa Tradition, please see the following two articles explaining the nature and function of NKT ordination and the authenticity of its lineage. There you will find the listing of all 253 vows of a fully ordained monk and see how they are not contradictory to the ten vows taken and kept by a monk or a nun in the New Kadampa Tradition.