The agency was adviced by the Supreme Court to follow the opinion of its chief while finalising its chargesheet.
CBI sources said the agency will book a former senior telecom official besides telecom companies.
The agency had registered a case against Shyamal Ghosh, the then Telecom Secretary when the ministry was headed by Pramod Mahajan, J R Gupta, who was the Deputy Director General (Value Added Services) and two Telecom service providers Airtel and Vodafone for alleged irregularities in grant of additional spectrum.
Sources said Gupta, who retired as Director, Bharat Sanchar Nigam Limited, has become an approver for the agency.
CBI had alleged in its FIR that the Department of Telecom increased the base spectrum for telecom companies from 4.4 MhZ to 6.2 MhZ during Mahajan's tenure from 2001 to 2003 and also allocated extra spectrum on subscriber-based criteria.
The case against the then DoT official, Bharti Cellular (now known as Bharti Airtel), and Hutchinson Max and Sterling Cellular (now known as Vodafone Essar) was registered under 120-B (criminal conspiracy) of IPC and under various sections of Prevention of Corruption Act, the CBI alleged.
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"The then Minister for Telecom and Communication (Pramod Mahajan) has been excluded since he expired," CBI had said but alleged he was a part of criminal conspiracy to allocate the additional spectrum in a "hurried" manner.
Both Bharti Airtel and Vodafone had, however, denied the allegation saying they had always maintained the highest standard of corporate governance and regulatory compliance.