The Supreme Court on Thursday transferred to the CBI the investigation in multiple cases against former Mumbai police commissioner Param Bir Singh over allegations of misconduct and corruption saying "a very murky affair is going on amid echelons of power".

A bench of justices S K Kaul and M M Sundresh said a thorough investigation is required to regain the faith of people in the state police.

"The exigencies in the advancement of principles of justice require the investigation to be transferred to CBI. We are not saying appellant (Singh) is a whistle-blower or anyone involved in this case is washed with milk, the bench said while allowing the appeal filed by Singh.

The bench also refused to revoke the suspension of Singh and said all future FIRs too will be transferred to the CBI.

"We are unable to accept the contention that an FIR is registered by those who had complaints against the petitioner. We are of the view that the state itself should have allowed CBI to carry the investigation.

"We are of the prima facie view that there is some concerted effort which needs the investigation by CBI. What is the truth, who is at fault how does such a scenario come to prevail is something which investigation must get into. CBI must hold an impartial inquiry into all these aspects," the court said.

The bench, however, noted it was not commenting on the merits of the allegations as it does not want the investigation to be influenced in any manner.

"We do not want the investigation to be influenced by the observation of this court. The High Court (Bombay) has treated this as a service dispute which it is not and thus we set aside the HC verdict. We allow the appeal and direct the probe into 5 FIRs and three PEs be transferred to CBI with all records.

"Such transfer to be completed within one week and all officials to extend full cooperation to CBI to try arrive at the truth," the bench said.

On departmental enquiry against Singh, the bench said it would be appropriate to await the result of the investigation now entrusted to CBI.

"We don't know if this is the end of the road or more FIRs may be registered arising from the period the petitioner had served in Maharashtra. If any further FIRs are registered that too shall be transferred to CBI. Needless to say we are not revoking the suspension. This order shall continue subject to any legal remedy as may be available to the appellant", the bench said.

At the outset, Singh's counsel, senior advocate Puneet Bali, submitted that an independent probe by CBI is necessary to ascertain the truth in the case.

"My police officers were called and asked to collect 100 crores from bars etc for the then Home Minister. The police officials who complained against me are being reinstated. The cases filed by Maharashtra government is a clear case of victimisation since this was based on baseless allegations," he said.

Additional Solicitor General K M Nataraj, appearing for CBI, argued that allegations against Singh are connected with the ongoing investigation against former home minister Anil Deshukh and the case should be handed over to the CBI for thorough investigation.

"The issue needs to be probed by the CBI for a thorough and impartial probe. If any other agency also probes this along with CBI then it may create hurdles and overlapping of subject matter. There cannot be a parallel investigation," Nataraj said.

Senior advocate Darius Khambata, appearing for the Maharashtra government, opposed the transfer of investigation to the CBI and said it would then demoralise the police force of the state.

"Param Bir Singh seeks to adopt the mantle of a whistleblower now after being at the head of this system. He writes this letter to the Chief Minister and somehow he thinks that this letter will grant him some kind of immunity," Khambata said.

The apex court at this juncture said, "No, he is not claiming any immunity."

"He says investigate everything against me. Here a very murky affair is going on amid echelons of power on who should investigate. He is not saying quash the FIR. Let me make it very clear that I am not treating Param Bir Singh as a whistleblower. These are fallouts when people fall upon.

"Therefore, a thorough investigation here is also in the interest of the state. It is reflecting on the state where the home minister and the police commissioner are involved in serious allegations," Justice Kaul said.

Khambata contended that the only reason for CBI probe is to have a thorough and impartial investigation and they say it concerns extortion of money from dance bars etc.

All this is based on media reports, he said.

The bench then said, "Media reports don't bother us. Yesterday the political dispensation of the Maharashtra government made statements about how they may not get a fair hearing at the hands of the judiciary and it was in press today and we read it. This has become a habit. We have also got used to handling them. But this has not bothered us. We throw them in the dustbin where they deserve to be thrown."

Singh is facing multiple cases of extortion, corruption and misconduct, and was removed from the post of Mumbai police chief over his alleged mishandling of the Antilia bomb scare case.

The top court had granted him a major relief on November 22 when it directed the Maharashtra Police not to arrest him in criminal cases lodged against him, and wondered if he was being hounded for filing cases against police officers and extortionists, "what could happen to a common man".

The Maharashtra Police had earlier told the apex court that Singh cannot be considered a "whistleblower" under the law as he chose to speak out against alleged corruption involving former state home minister Anil Deshmukh only after he was transferred.

Seeking dismissal of Singh's plea for a CBI probe into the entire matter and against any coercive action by the state, the Maharashtra government had filed an affidavit in the apex court and said that the ongoing investigation in criminal cases against the former top police officer should not be interfered with.

Prior to this, the Bombay High Court had dismissed Singh's petition seeking quashing of inquiries initiated against him by the Maharashtra government, and said he can approach the Central Administrative Tribunal, holding it was a service matter. It had rejected his claim that the government's action was a consequence of his allegations of corruption against Deshmukh.