A day after the premier health institute denied his claim, Dr Sudhir Gupta said, "I stand by what I said".
"How do they know there is no pressure on me Who were they to clarify that there is no pressure on me What was the hurry to call a press conference," he said.
He was asked about AIIMS rejecting allegations levelled by him.
"Not only the post mortem of Sunanda Pushkar but in a number of cases, post mortem reports were finalised by me as per the principle and practise of medicine and as per its ethical and legal norm. I have never succumbed to any pressure in my life," Gupta told PTI.
He said all his reports are bonafide.
Rejecting the charge of Gupta, who headed a three- member team that did the post morten on the body of Pushkar, who died in mysterious circumstances in a hotel in January this year, AIIMS had said there was no evidence that any pressure from outside was put on him (Sudhir Gupta) to alter the autopsy report.
Sunanda (52) was found dead in a 5-star hotel in South Delhi on the night of January 17, a day after her twitter spat with Pakistani journalist Mehr Tarar over an alleged affair with Tharoor.
The autopsy report had mentioned more than a dozen injury marks on Sunanda's both hands and an abrasion on her cheek which suggests a "use of blunt force", besides a "deep teeth bite" on the edge of her left palm. Viscera samples were preserved after the autopsy at AIIMS and were sent to CFSL for further tests.
The CFSL report hinted at drug poisoning but its findings were not conclusive enough to file an FIR in the case, according to police.