The CBI on Tuesday placed before the Supreme Court the report of the TRAI which said it was not possible to predict with certainty the precise value of 2G spectrum that would have emerged in auction between 2001-08.

The report, which was placed before a bench comprising of Justice GS Singhvi and Justice HL Dattu, said it was a "tricky" exercise to estimate the annual value of spectrum for eight years.

The bench, which was hearing the bail pleas of two of the accused in the 2G spectrum scam, had yesterday said that it would like to go through the TRAI report after senior advocate Ram Jethmalani had submitted that telecom regulator in its report had given a finding that there was no loss in the allocation of spectrum.

The report said "retrospectively estimating annual value of spectrum in the 1800 MHz band for eight years between 2001 and 2008 is a tricky exercise at the best of times.

Access to data is crucially important, but equally, if not more important is access to business plans and forecasts of service providers who invest in the market.

"We do not have access to the latter information and even the data that we have is inadequate, as documented in our report. We, therefore conduct the exercise of estimating market value of spectrum under severe data constraints and a changing technological environment".

Asked whether CBI''s case becoming weak due to TRAI's report that there was no loss to the government due to spectrum allocation in 2008, TRAI Chairman JS Sarma said that "the experts have given the range of values but they could not arrive at any definitive figure."

Sarma, however, asserted that this is not TRAI but experts's report and they have indicated the reasons why they didn't arrive at any definite value which is in the report.

Giving the economic models applied for calculating the values of spectrum, the report said "for the terminal year, the range of estimates of the value is between around Rs5,500 crore to Rs9,500 crores and the range narrows for earlier periods".

"Given that we are trying to estimate a value that bidders would have placed had spectrum been auctioned, it is not unreasonable to expect variation between different approaches. Given the scant data that is available to us, it is also not possible to estimate the standard errors or the confidence intervals for our estimate," the expert committee said in the report.

"It is therefore not possible to predict with certainty the precise values of spectrum that would have emerged in auction. The risk of error in the estimates increases since the exercise is carried out retrospectively and with meagre data.

"We are however confident of the analytical foundations of the methods and their appropriateness to the task. However, we cannot rule out the possibility that armed with richer data we could improve the reliability of our estimates. Our results may be interpreted in this spirit," the report said.