"The investment was of 800 million USD which is Rs 3,500 crore (approx). The FIPB approval (by the then Finance Minister) was a mistake. This is under investigation," the Investigating Officer in the case told Special Judge O P Saini.
The agency said it was investigating as to how Chidambaram had given foreign investment promotion board (FIPB) approval in the Aircel-Maxis deal in 2006.
It contended that Finance Minister was competent to give approval of upto Rs 600 crore but Chidambaram gave the approval which was worth 800 million USD, approximately Rs 3,500 crore.
It said that the matter should have been referred to the Cabinet Committee on Economic Affairs (CCEA) and they are probing as to how Chidambaram gave the approval.
"Your (judge) query was on FIPB approval. We are showing documents which show the power of the then Finance Minister. Power was vested in the then Finance Minister to give FIPB approval of upto Rs 600 crore.
"For investment of over Rs 600 crore, CCEA was competent to give approval. This is under investigation and we have not concluded the probe on this aspect yet," CBI prosecutor K K Goel said.
The agency had told the court in its chargesheet in the case that Mauritius-based M/s Global Communication Services Holdings Ltd, a subsidiary of Maxis, had sought approval for USD 800 million for which CCEA was competent to do so.
In its chargesheet, CBI had named former Telecom Minister Dayanidhi Maran, his brother Kalanithi Maran, T Ananda Krishnan, Malaysian national Augustus Ralph Marshall and four firms -- Sun Direct TV Pvt Ltd, Maxis Communication Berhad, South Asia Entertainment Holding Ltd and Astro All Asia Network PLC -- as accused in the case.
They have been charge sheeted for the offences punishable under section 120-B (criminal conspiracy) of the IPC and under relevant provisions of the Prevention of Corruption Act.
On being asked by the court about the role of Kaveri Maran, wife of Kalanithi Maran who has been charge sheeted by the CBI in the case, the agency said that although she was holding 82 per cent share in accused firm Sun Direct TV Pvt Ltd but as per the documents, every decision was taken by her husband.
"Documents do not reveal about her role directly. If the court give us further task, we will certainly investigate this aspect," the CBI said.
The court has now fixed the matter for further arguments on October 13.
On September 11, the CBI had told the court that former Telecom Minister Dayanidhi Maran had "pressurised" and "forced" Chennai-based telecom promoter C Sivasankaran to sell his stakes in Aircel and two subsidiary firms to Malaysian firm Maxis Group in 2006.
The Malaysian firm was favoured by Maran and granted licence within six months after the take over of Aircel in December 2006, it had said.
Ex-Telecom Secretary J S Sharma, who has died, has also been named in the CBI's charge sheet. However, his name has been put in a column of the accused against whom trial cannot proceed.
The 72-page charge sheet includes the names of 151 CBI witnesses and a set of 655 documents, on which the agency has relied upon in its investigation.