Tata Sons Limited on Thursday said a letter written by ousted chairman Cyrus Mistry to the group had made “unsubstantiated claims and malicious allegations”. In a statement, the group said it was a “matter of deep regret” that the letter, which was marked confidential, was made public “in an unseemly and undignified manner”.

The group said it will respond to Mistry’s claims “in an appropriate manner”. “It is unfortunate that it is only on his removal that allegations and misrepresentation of facts are being made about business decisions that the former Chairman was party to for over a decade in different capacities,” the statement said, adding that the allegations would be proved wrong as and when they were made public.

“Trustees of the Tata Trusts were increasingly getting concerned with the growing trust deficit with Mr Mistry,” the statement further said. In his letter, Mistry had claimed the conglomerate faced $18 billion (Rs 1.15 lakh crore) in write-downs or reduction in value of assets. The letter said he had inherited “debt-laden” ventures of Indian Hotels Co, Tata Motors Ltd’s passenger-vehicle operations, Tata Steel Ltd’s European business, and part of the group’s power unit and its telecommunications subsidiary during his tenure as chairperson.

On October 24, the board decided to push Mistry out after a massive fallout, with Tata’s shares falling and the company anticipating legal action by the former executive. Ratan Tata has taken over Mistry’s post temporarily, the company said. The Tatas also filed caveats seeking a notice from Mistry “fearing legal action” against their move to dismiss him from the post after four years. A caveat is a preventive measure that disallows courts from hearing matters without both parties being notified about them first.