The Joint Parliamentary Committee examining the 2G scam has sought to know from comptroller and auditor general Vinod Rai as to how he quantified the losses in the spectrum allocation at Rs1.76 lakh crore.

Rai will brief the JPC, chaired by Congress leader PC Chacko on the allocation and pricing of telecom licences and spectrum during 1998 to 2009.

The findings triggered a political storm and subsequent events led to the resignation of the then telecom minister A Raja.

"Today the talk is of a Rs1.76 lakh scam. We want to know from the horse''s mouth how he had arrived at the figure," Chacko said after the last meeting of the committee on May 18.

Telecom minister Kapil Sibal had dubbed "utterly erroneous and without any basis" the estimated loss of Rs1.76 lakh crore, arrived at by the CAG on account of 2G spectrum allocation.

According to the CBI charge sheet in the 2G spectrum allocation case, the loss to the exchequer is pegged at Rs30,984 crore.

The JPC has decided to call CBI director AP Singh to brief on the 2G case at its meeting on June 7, while the finance secretary, chief of Enforcement Directorate, and Telecom Regulatory Authority chairman JS Sarma will make presentations on the issue.

Sarma had begun his presentation on the functioning of TRAI and its role in the telecom sector which was inconclusive and would continue on June 8.