"I would request you to take immediate and appropriate action against such unlawful misconduct of the officer concerned.

"My staff and I have always made ourselves available for any kind of inquiry and investigation but the recent behaviour of the officers towards my staff is a matter of serious concern to any law abiding citizen.

"Please look into the matter personally and ensure that the unvarnished truth comes out in this case."

Tharoor said he had "complete trust and faith" in Delhi Police and that he was committed to "fully cooperating with the investigations to ensure the timely completion of the inquiry".

The letter became public knowledge a day after Delhi Police announced that Pushkar, found dead in a hotel a year ago, was poisoned to death.

Bassi said Tuesday that this was the conclusion of the final medical report of the All India Institute of Medical Sciences, which had conducted Pushkar's autopsy.

Pushkar, 52, died in mysterious circumstances Jan 17 last year. Tharoor was then a minister in the government of then prime minister Manmohan Singh.