Taking the 2G probe to the doorstep of the Prime Minister's Office, PAC is likely to ask Principal Secretary to the PM, T K A Nair, and Cabinet Secretary K M Chandrasekhar to appear before it this fortnight in connection with the telecom scam.

Sources said Parliament's Public Accounts Committee, headed by senior BJP leader M M Joshi, has called Nair, Chandrasekhar and CBI director A P Singh to depose before it on April 15-16 on the 2G spectrum allocation scam.

These three are likely to be the last ones to be called by the present committee, whose term comes to an end on April 30. The PAC secretariat is already in the process of filing its report and is expected to complete it by this month-end.

While many new faces will be there in the new PAC, Joshi will continue to be its chairperson. The new PAC is also likely to carry out probe into some aspects of the 2G scam, which, according to the Comptroller and Auditor General, caused a presumptive loss of Rs 1.76 lakh crore.

The Committee is likely to scrutinise the role of the Prime Minister's Office (PMO) in the controversial allocation of 2G spectrum in 2008.

In this regard, Nair and Chandrasekhar are likely to be asked on the communications between the Finance Ministry, the Department of Telecom and the PMO on the allocation of 2G spectrum.

"After listening to the views of the then Finance Secretary (and now RBI Governor Duvvuri Subbarao), it is necessary to get the views of the Cabinet Secretary and the Principal Secretary to the Prime Minister," a source said.

Subbarao, who was the Finance Secretary when the 2G spectrum allocations were made in January 2008, had appeared before the PAC on February three.

In an affidavit filed in the Supreme Court, the government had said that on the issue of 2G allocation the finance secretary had raised certain queries on November 27, 2007 regarding the entry fee. A reply to this was given by the telecom secretary on November 29, 2007.

Sources said the two top officials could also be asked questions based on the Prime Minister's recent statement that the Finance Ministry and Telecom Ministry had concurred on the issue, as a result of which he did not press the matter further.

The CBI chief, who had appeared before the PAC on February 15, had recently met Joshi. Sources said it was a prelude to his appearance before the Committee.

The CBI has recently filed a charge sheet in a special court on the 2G scam which named three companies - Unitech, Reliance Communications and Swan Telecom, besides former Telecom Minister A Raja.