Expanding its probe to cover the NDA regime, the Central Bureau of Investigation on Saturday registered a case against Shyamal Ghosh, who was Secretary in the Telecom Ministry headed by late Pramod Mahajan, and two Telecom service providers Airtel and Vodafone for alleged irregularities in grant of additional 2G spectrum.

Immediately after registering of the case, CBI teams searched the offices of the two major telecom companies and residences of Ghosh and J R Gupta, who was the Deputy Director General (Value Added Services) in the Telecom Ministry during Mahajan's tenure.

The searches were carried out at the offices of Vodafone in Mumbai and Airtel in Gurgaon, National Capital Region. Responding to the raids, both Bharti Airtel and Vodafone said they had always maintained the highest standard of corporate governance and regulatory compliance. CBI had ordered a Preliminary Enquiry to look into the allocation of spectrum under Mahajan to certain companies beyond the prescribed limit. Defending the then NDA cabinet's decision on spectrum allocation, BJP on Saturday termed CBI's move to register cases against officials on alleged irregularities in the 2G scam as a "political conspiracy".

BJP spokesperson and MP Prakash Javadekar said the CBI is being used as a tool by the Congress-led UPA government. He said, "This case has been filed to prevent a probe against then finance minister P Chidambaram."