In a note sent to the DoT for comments, the Comptroller and Auditor General of India (CAG) is believed to have put undue benefits accruing to Bharti Airtel because of the DoT at Rs 204.35 crore, sources said.
"Airtel was providing 3G services and earning revenues from 20 service areas and hence the DoT should have applied higher rate of SUC for all of them instead of limiting it to only 13 service areas," the sources said citing a note sent by CAG's Post and Telecommunications Audit Office to the DoT.
"By not doing so, the DoT had provided undue benefits of Rs 204.35 crore to Bharti Airtel on SUC," they added.
Airtel is providing 3G services in Kerala, Madhya Pradesh, Gujarat, Kolkata, Maharashtra, Haryana and UP East where the company did not win any spectrum.
Airtel used airwaves of other companies -- Vodafone and Idea Cellular -- for the services under a roaming agreement.
The 3G roaming agreement is sub-judice where DoT has termed it illegal but the three companies have argued that the pact is legal.
No immediate comments were received from Bharti Airtel.
The CAG is of the view that company should be made liable to pay a proportionate sum of the bid amount paid by the successful bidder in the seven service areas for the period it has used 3G spectrum, sources said.
"These charges would work out to Rs 521.33 crore for the period up to March 2013," it added.