The CBI, which was asked by the Central Vigilance Commission to do a 'discreet' ground verification of allegations of Sibal's nexus with private oil and gas operators, in its preliminary report, alleged "gross abuse and misuse of public office by Sibal," highly placed sources said.
"The CBI is yet to formally approach the government for permission for a thorough probe," Oil Secretary R S Pandey told reporters. Sources, however, said that CBI would be moving government for permission shortly.
The preliminary report also talked of his "nexus with private parties" and his "obtaining pecuniary advantage in award of contracts and supply of information of sensitive data of resources."
However, neither the CVC nor the CBI have said anything on the allegations of his seeking favours from RIL in lieu of approving higher capital expenditure at Mukesh Ambani-run firm's Krishna Godavari basin gas field.
CVC last month sought CBI help when its clearance was sought for giving an extension of service to Sibal as Director General of Directorate General of Hydrocarbons.
Sibal's term at the DGH ended on October 31.
Sources said the anti-corruption body's report stated that prima facie a "vigilance angle" has been established in certain cases of extension of contracts by Sibal.
Govt official fears for life from Anil Ambani group
'Threat to life' claims: Anil Ambani group may sue Sibal
Sibal may not continue as oil regulator
Sibal bids farewell to DGH, returns to OIL
Ex-oil regulator Sibal goes on long leave from OIL