Mistry was removed as chairman of TCS early in November.
Mistry's ouster has triggered a public spat between him and Tata Sons, which has also pushed some of Mistry's closest aides out of the group.
Tata Group is seeking to remove Cyrus Mistry as chairman of its biggest listed unit, weeks after ousting him as head of India's largest conglomerate.
1 software services firm, Tata Consultancy Services (TCS), a majority-owned unit of Tata Sons, said on Thursday it received a letter from Tata Sons nominating Ishaat Hussain as interim chair of TCS in place of Cyrus Mistry.
Hussain will hold office as Chairman until a new chairman is appointed in his place.
IiAS further says that in the imbroglio that has erupted, the Tata group "has left itself with no option but to push for his (Mistry's) removal from the boards of group companies". Mistry was the Chairman of Tata companies such as Tata Steel, Tata Consultancy Services, Tata Motors, Indian Hotels Co Ltd (IHCL), Tata Power Company, Tata Global Beverages, Tata Chemicals, Tata Industries and Tata Teleservices.
After having worked with the group for several years, Hussain was rewarded with an executive board position at Tata Sons in July 1999, before taking over as finance director of the holding company in July 2000. He had also rebutted reports of mishandling a dispute with Japan's NTT DoCoMo and said that Ratan Tata new of all decisions regarding the telecom venture. After Cyrus Mistry's removal, his predecessor Ratan Tata was back at the helm as chairman after almost four years. Later, he was on the board of the Indian Tube Company in 1981, which later paved his entry into Tata Steel in 1983 after the former was merged with the steel arm. "This hard decision, made after careful and thoughtful deliberation, is one the board believes was absolutely necessary for the future success of the Tata Group", the interim chairman wrote to employees of $100 billion Group.