"It's time that Defence Minister A.K. Antony and other senior leaders in the Congress break their silence on the mysterious death of Tharoor's wife," Achutanandan said in a written statement issued here.
Pushkar was found dead in her room at a five-star hotel in Delhi in January. The death triggered a controversy in the media especially because of reports of differences between Pushkar and Tharoor.
Achutanandan said that as per law, if a woman dies an unnatural death within seven years of her marriage, a case should be registered against her husband.
"Their marriage lasted under three years and hospital authorities and police have already gone on record stating that her death was a mystery. Till now, no case has been registered against Tharoor and the silence of Antony and the central government is baffling," he said.
Achuthanandan's statement came after a complaint filed by Tharoor Tuesday with poll officials over the slander unleashed against him by M. Vijayakumar, former Kerala assembly speaker and a senior leader of the Communist Party of India-Marxist and also a close aide of Achuthanandan.
At an election meeting, Vijaykumar reportedly said Tharoor could be given a doctorate in "violence against women".
Following Tharoor's complaint, poll authorities have now asked the CPI-M leader to respond to the charge.
Tharoor Tuesday also filed his nomination papers as the Congress candidate from the Thiruvananthapuram Lok Sabha seat, which he won in the 2009 polls.