By Aditi Shah

MUMBAI (Reuters) - Ousted Tata Sons Chairman Cyrus Mistry said on Tuesday any "insinuations" he mis-handled a dispute with Japanese telecoms firm NTT DoCoMo Inc were baseless, ratcheting up a war of words with the Tata Sons board.

Sources close to the matter have said one of the reasons for Mistry's ousting was his handling of a long-running dispute with DoCoMo, Tata Sons' partner in a telecoms joint venture in India.

Mistry's office said in a statement all decisions related to the dispute were taken with the unanimous approval of the Tata Sons board, as well as the approval of Tata family patriarch Ratan Tata and Tata trustee N.A. Soonawalla.

"The insinuations are being imagined and this (DoCoMo) matter is sub-judice," said a Tata Sons spokesman, adding the company would not comment any further on the matter.

Mistry's statement comes a week after he was ousted as chairman of the $100 billion steel-to-software conglomerate in a boardroom coup that saw Ratan Tata return as interim chairman.

Tata Teleservices, a Tata group company, and DoCoMo have been locked in a long tussle over the latter's move to exit a partnership the two companies formed in 2009. The dispute is still being dragged out in courts.

(Reporting by Abhirup Roy and Aditi Shah; Editing by Euan Rocha and Mark Potter)