Ousted Tata chairperson Cyrus Mistry on Tuesday filed a suit against Tata Sons in the National Company Law Tribunal, PTI reported. The petition was filed against the oppression and mismanagement of Tata Sons under Section 241 of the Companies Act.

Investment firms controlled by Mistry’s family moved the NCLT in Mumbai against the company on Tuesday. The court will hear the petition on December 22.

In a statement, Tata Sons said that it would contest the allegations made in the suit. “Despite, Cyrus Mistry’s recent assertions that it is not a personal issue, it is evident that it always has been for him a personal issue which reflects his deep animosity towards Ratan Tata,” the statement said.

The statement further said Mistry’s removal from his post was approved by an overwhelming majority of its directors. “It is unfortunate that Mr Mistry has not been able to graciously accept the decision of the very same Board that appointed him,” it added.

Mistry had stepped down from all Tata Groups on Monday saying it was time to be more “incisive in securing the best interests of the Tata Group”. In his resignation letter, Mistry accused Ratan Tata of staging “an illegal coup” against him on October 24. “In order to be more effective, serve the objective of governance reform, and to regain lost ethical ground, I have decided to shift from the forum of the EGMs to a larger platform and also one where the rule of law and equity is upheld,” he said.

Following Mistry’s resignation, Tata Sins released a statement saying the public announcement of his resignation was a “deliberate strategy” on Mistry’s part. The company also said Mistry’s allegations made in the letter were “baseless, unsubstantiated and malicious” in nature.

Mistry was removed from the post of chairman of the company on October 24, and Ratan Tata took over as the interim chief. The company had earlier accused Mistry of misleading the 2011 selection committee set up to appoint Ratan Tata’s successor. It alleged that Mistry took advantage of his position to “systematically” dilute the representation of Tata Trusts on the boards of group companies.