Tata Sons demanded former chairman Cyrus Mistry return all confidential information and documents regarding the company in his possession, in its second legal notice in as many days.
The letter, sent by Tata Sons' lawyers, further demanded that Mistry sign a letter pledging not to disclose any confidential information regarding the company, including to affiliates, relatives and family members.
"We have credible information that you have wrongfully and dishonestly taken movable property being confidential information," said the letter, a copy of which was seen by Reuters.
The notice comes after Tata Sons, the holding firm for the $100 billion Tata conglomerate, on Tuesday accused Mistry of breaching confidentiality rules, and said it would take legal action against him.