Attorney General Goolam Vahanvati, CBI Director A P Singh and Law Secretary D R Meena are expected to appear before Parliament's Public Accounts Committee tomorrow to give evidence in the probe into the 2G spectrum allocation scam.

The PAC, chaired by senior BJP leader Murli Manohar Joshi, is likely to quiz Vahanvati about the legal opinions he may have given to the Telecom Ministry when he was Solicitor General in UPA-I.

The Attorney General has been made a witness by CBI in its chargesheet filed before the special court in the 2G scam.

The CBI director has been asked to appear before the PAC for the second time. Singh had appeared before the PAC on February 15 and told the panel that it was wrong to say that the 2G spectrum allocation had caused zero loss to the national exchequer.

Singh also had a one-to-one meeting with Joshi last month. The CBI is investigating the 2G spectrum case and has already filed a chargesheet.

The Committee has also called Cabinet Secretary K M Chandrasekhar and Principal Secretary in PMO T K A Nair to depose before it on April 16.

The April 15-16 sessions will be the last hearings by the outgoing PAC.

The PAC headed by Joshi is already in the process of filing its report on the 2G spectrum case and is likely to complete it before its term ends on April 30.

The new PAC, in which Joshi will continue to be the chairperson, will take charge on May 1 and is set to carry on the probe into the anomalies in 2G spectrum allocation.

Chandrasekhar and Nair have been asked to appear as the PAC is likely to scrutinise the role of the Prime Minister's Office (PMO) in the controversial allocation of 2G spectrum in 2008.

The two senior bureaucrats are likely to be asked questions on the communications between the Finance Ministry, the Department of Telecom and the PMO on the allocation of 2G spectrum.

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, after which he did not press the matter further.