The Apollo Hospitals have also filed a petition in the high court to appoint an independent medical board, if the Commission's terms of reference also cover an inquiry into the treatment given to Jayalalithaa.
"We feel the Commission is going beyond its terms of reference. The terms of reference for the Commission does not intend to go into the adequacy of the treatment given to Jayalalithaa. The inquiry is now changing towards a case of medical negligence," a person close to Apollo Hospitals told IANS.
The Apollo Hospitals had filed the petition on Tuesday and the matter is coming up for hearing on February 11.
The Commission had earlier turned down the request of Apollo to set up a medical board.
In an order issued detailing the terms of reference of the inquiry commission, the Tamil Nadu government had said it would "inquire into the circumstances and situation leading to the hospitalisation" of Jayalalithaa on September 22, 2016 and "subsequent treatment provided till her unfortunate demise" on December 5 that year.
Ever since Jayalalithaa's death, there have been allegations of foul play.