Tharoor said he had 'fully cooperated' with the police at every stage of the case.
He was reacting to reports broadcast on Monday by a recently launched television channel in this regard.
"I want to stress that I have fully cooperated with police. Police have investigated for the past three years. They have not so far been able to establish whether any crime has been committed or any murder has occurred," Tharoor told reporters in Thiruvananthapuram.
Police are the right and the most competent persons to respond, he said.
As a reporter of the channel tried to pose questions to him and alleged that he was physically manhandled, Tharoor said, "These people are not journalists. This is what they want. This is going to be their story. The new channel's effort is to get into limelight and increase its TRP."
Addressing the local media, Tharoor said, "As far as I am concerned, you are all professional journalists. This unfortunately is not an example of professional journalism," and added he was a strong advocate of freedom of expression.
Tharoor said the media has a very important role as a witness, but not a role of prosecutor, judge and executioner, "which is what as you are seeing somebody is do".
"There is a legal system in the country. There are constitutional rights for people in the country. There is a judicial system in the country. Let police conclude their work and go to courts and courts can come to conclusions. That is the way the system is supposed to work," Tharoor said.
Sunanda was found dead in a suite in a five-star hotel in South Delhi on January 17, 2014.
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