The former Telecom Minister has expressed willingness to appear before the panel and DMK members in JPC T R Baalu and T Siva have been pressing Chacko to call Raja as a witness.
On Friday, Raja had written to Lok Sabha Speaker Meira Kumar and Chacko making a strong pitch to appear before the JPC as a witness claiming that he has been "condemned unheard".
Vahanvati was then the Solicitor General.
Raja has also been blamed for the 2G scam by other witnesses before the special CBI court.
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Chacko is apparently against calling Raja as a witness. He has told members that as an accused Raja has legal protection and cannot make fresh revelations before any committee. Therefore, there was no point in calling Raja.
Raja's request has come when the three-month-long Budget session has just commenced.
Congress members in the JPC are against calling Raja as a witness as his deposition could be used by opposition members, including BJP and the Left, in cornering the government. Raja has maintained that he had kept the Prime Minister's Office and others informed about his decisions on 2G licencing issue.