The BJP and the Left Front on Tuesday asked Congress MP Shashi Tharoor to resign from the Lok Sabha after Delhi Police said that his wife Sunanda Pushkar was poisoned to death.
Former chief minister V.S. Achuthanandan said the Congress should publicly apologise for "protecting" Tharoor when he was a minister in the Congress-led central government.
"Now with a murder case registered, Tharoor should resign and make himself available for the probe," the Communist Party of India-Marxist leader said in a statement.
Kerala BJP president V. Muraleedharan asked Tharoor to resign from the Lok Sabha. Sunanda Pushkar was murdered: Delhi Police
"The Congress should apologise to the people for fielding him (in the Lok Sabha polls)," said Muraleedharan.
Kerala Chief Minister Oommen Chandy declined to comment on the case.
Tharoor retained the Thiruvananthapuram Lok Sabha seat with his margin of victory dropping from close to a lakh in 2009 to around 15,000 votes.
BJP veteran O. Rajagopal edged out the Left candidate to the third place.
Delhi Police chief B.S. Bassi said on Tuesday that they had registered a murder case against "unknown persons" after the final medical report said Pushkar was poisoned and died an unnatural death.
Later, Tharoor on Tuesday said he was "stunned" by the Delhi Police's claim that his wife Sunanda Pushkar was murdered by poisoning. The former Union minister also demanded "comprehensive" investigation into Pushkar's death.
"I am stunned to hear that the Delhi Police have filed a case of murder against unknown persons in the demise of my late wife Sunanda. Needless to say, I am anxious to see this case is investigated thoroughly and continue to assure the Police of my full co-operation," a statement released by Tharoor said.
"Although we never thought of any foul play in the death of my wife, we all want that a comprehensive investigation be conducted and that the unvarnished truth should come out. In the meantime, I join all members of Sunanda's family in asking for full information about the basis on which the Police have come to this conclusion," the statement said.