Sushant Singh Rajput's father on Thursday urged the Supreme Court to confirm the transfer his son's suicide case to the CBI and direct the Mumbai police to render all assistance to the central probe agency.

Mumbai Police was "not investigating the matter properly", Krishna Kishore Singh alleged in his written submission to the apex court.

The Bihar government and Rhea Chakraborty, against whom Krishna has filed an FIR in Patna for allegedly abetting Rajput's suicide, also filed their written submissions to the top court on the actress' plea seeking transfer of the FIR to Mumbai.

Famous actor Raput, 34, was found hanging from the ceiling of his apartment in suburban Bandra in Mumbai on June 14.

In the submission, settled by senior lawyer Vikas Singh, Krishna referred to various judgements and said, it would be expedient in the interest of justice for this Court to confirm the reference to the CBI as justified and further direct Maharashtra Police at Mumbai to render all assistance to agency in the matter.

He further said that he was certain that the Mumbai police was not investigating the matter properly and were continuing with inquest proceedings indefinitely, when clearly under S.174 CrPC the inquest report has to be prepared forthwith basically to determine the cause of the death and as to whether there were any suspicious circumstances surrounding the said cause or not...

Bihar Police has the jurisdiction to probe his FIR, Krishna said, adding that the role of Mumbai Police was completely dubious as an inquest report should have been submitted forthwith, and even if it is to be assumed that the police was doing a preliminary inquiry in the matter, it cannot continue for more than seven days.

He accused Mumbai Police of not investigating Sushant's prior messages or acknowledge the fact that he was in some kind of problem.

"Mumbai police instead of investigating prior messages sent by the deceased's family on WhatsApp on February 19 and 25, 2020, has taken a stand that no written complaint was registered and thus no action whatsoever was taken in that regard by the Mumbai Police. Such inexplicable explanation is contrary to Section 154 (1) of CrPC which clearly states that any information (even if given orally) of cognizable offence ought to be considered for registration of FIR as held in", his submission said.

Krishna alleged that Chakraborty was examined four days after the incident, giving her ample time to destruct the evidence and influence the witnesses.

He also alleged that Rhea was hand in glove with an important witness, who even after registration of FIR shared e-mails with her.

In its submission on Thursday, the Bihar government said that Mumbai Police neither registered an FIR on the actor's suicide nor did it extend any support to Patna Police for investigating the case on "account of political pressure".

"It is apparent that it is on account of political pressure in the State of Maharashtra that neither the FIR has been registered by the Mumbai Police nor did they extend any cooperation to Bihar Police in discharging their obligation to conduct investigation expeditiously," said Bihar government, in its submissions filed through lawyer Keshav Mohan.

Chakraborty however said that the transfer of investigation to the CBI at the behest of Bihar Police was without the state's jurisdiction in the case.

The apex court had on August 11 reserved its order on Chakraborty's plea and asked the parties concerned to file their written submissions by Thursday.

On August 11, the Bihar government told the Supreme Court that political clout has not allowed Mumbai Police to even register an FIR in the Sushant Singh Rajput's suicide case, even as the Maharashtra government maintained Bihar completely lacks jurisdiction in the matter.

The FIR in Patna has been registered against Chakraborty and others for alleged offences under various sections of the Indian Penal Code, including 306 (abetment of suicide), 341 (punishment for wrongful restraint), 342 (punishment for wrongful confinement), 380 (theft in dwelling house), 406 (punishment for criminal breach of trust) and 420 (Cheating and dishonestly inducing delivery of property).