The former Lok Sabha Speaker, whose candidature for Presidentship is being pushed by AIADMK and BJD, said he had received "promises of support from senior leaders of non-Congress parties, including those in the NDA".
He sent his resignation letter to party chief Sharad Pawar soon after Janata Party President Subramanian Swamy, a constituent of NDA, met him apparently to pledge support.
"I hereby tender my resignation from the primary membership of NCP with immediate effect. I place on record my deep gratitude to the President, other office bearers and rank and file of NCP for the courtesies extended to me by them at personal level while I was a member of the party," he wrote in his resignation letter.
In a statement, Sangma said he had "no option but to resign" from NCP "without any personal intent whatsoever of embarrassing the party and its leadership".
Talking about the circumstances in which he had to quit, the 64-year-old leader said, "disinclination of the NCP to endorse my candidature amounts to a denial of the aspirations of the tribals of the country."
He noted that his candidature had been projected by the Tribal Forum of India and he cannot "ignore the feeling of the tribals that Raisina Hill (Rashtrapati Bhavan) should not continue to be a distant dream for them." (MORE)