"Who is he? If he knows the murderer, then let him tell the police," Tharoor said to the media.
On Saturday, Swamy had alleged that Tharoor knew about his wife's killer and that he has been trying to cover up the case by lying. "Tharoor did not kill her, but he knows who killed her and facilitated her killing. He told lies and tried to cover up," he had said.
According to reports, the Delhi police has issued a legal notice to Tharoor, asking him to join the murder probe of his wife at the earliest.
Pushkar, who married Tharoor in 2010, had checked into The Leela Hotel in Chanakyapuri a day before her death on January 17, 2014.
Tharoor's aides said the couple had checked into the luxury hotel because of renovation work at his New Delhi bungalow.
Prior to her death, Sunanda was embroiled in a spat with Pakistan-based journalist, Mehr Tarar, whom she accused of having an affair with her husband.
Image: Congress leader Shashi Tharoor with his wife Sunanda Pushkar
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