New Delhi, Jan 21 (IANS): A PIL was filed Tuesday in the Delhi High Court seeking its intervention in the ongoing investigation in the mysterious death of Congress MP Shashi Tharoor's wife Sunanda Pushkar.

The Public Interest Litigation, filed by NGO Anti Corruption Front, said investigating agency was biased in probing the case so there was no positive and constructive development in the case and in such a situation, there was cause and reason for the interference of the court into the ongoing investigation.

Filing the plea through advocates Deepak Prakash and Subhas Chandra, the NGO said police had registered an FIR almost a year after the incident, despite clear guidelines laid down by the Supreme Court and high courts that on receiving information disclosing commission of a cognisable offence, police should register an FIR without any delay.

"In the present matter, police registered an FIR almost after 342 days of the occurrence of the crime," the plea said.

It added that Pushkar died under mysterious circumstance, her body carried more than 10 injury marks and the reason for the death was mentioned as poisoning.

"Even the investigating agency found it is a clear case of murder but till date it is in dark. Even a long one year passed after the incident occurred in a five star hotel of the capital no convincing conclusion is come out with regards to the accused persons who planned and executed the murder," the PIL stated.

Delhi Police have constituted a special investigative team to probe the death of Pushkar after registering an FIR in the case Jan 1. The FIR was filed based on Pushkar's third autopsy report by the AIIMS medical board.

Police Monday questioned Lok Sabha MP Tharoor, a former UN diplomat and formal union minister.

The plea filed against CBI, home ministry and Delhi Police said "Police commissioner is duty bound to explain the reasons for such serious dereliction of duty and latches on the part of his department in not registering an FIR in a case death of a lady within seven years of her marriage in mysterious circumstances."

Saying there was no credibility for the ongoing investigation, the plea said the accused in the case are very powerful and influential people, who have the capacity to influence police.

"The facts of the case indicate that the top police officials were influenced and the accused have succeeded in their efforts by keeping the present case in cold storage for a period of one year. So, the investigation of the case has not been proceeding in the proper direction, if the present investigation is continuing in this manner no truth would come out," said the plea.

It added: "The case clearly depicts the insensitivity of the Delhi Police and its pachydermatous indifference to the suffering of a common man."

Pushkar was found dead in a luxury hotel here Jan 17, 2014. Police have said she was poisoned to death.