Comptroller and Auditor General Vinod Rai on Monday appeared before the Joint Parliamentary Committee (JPC) examining the 2G spectrum scam to explain how the government auditor quantified the losses in the spectrum allocation at Rs 1.76 lakh crore.

Rai was asked to brief the Committee, chaired by Congress leader P C Chacko, on the allocation and pricing of telecom licences and spectrum during 1998 to 2009.

The CAG, in a report to Parliament last year, had pegged the presumptive loss to the exchequer on 2G spectrum allocation at Rs 1.76 lakh crore.

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 Rs 1.76 lakh crore 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 Rs.

1.76 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 Rs 30,984 crore.

Earlier this year, Rai had made a similar presentation before the Public Accounts Committee (PAC) of Parliament on how he arrived at the figure.

PAC examines the CAG reports and tables its findings to Parliament.