The CBI fired the prosecutor, AK Singh, who is allegedly heard offering legal advice to Mr Chandra.
Last week agency's chief, Ranjit Sinha told a parliamentary committee that's studying the scam that the CD was delivered anonymously ten days ago to a senior official. The agency has said it has no idea who recorded the conversations.
Mr Chandra had released a statement flatly denying allegations of collusion. (Read statement here)
The taped conversation allegedly took place in September last year, said CBI sources, which has the agency wondering why the CD was delivered so many months later.
Unitech had a mobile phone joint venture with Norway's Telenor and its license was among the 122 cancelled by the Supreme Court last year. Telenor is in the process of dissolving the joint venture.
The telecom scam, evaluated by the government's auditor at 1.76 lakh crores, was allegedly engineered by A Raja when he was Telecom Minister to give out-of-turn licenses and free second-generation airwaves to companies like Unitech.
Mr Raja and Mr Chandra are being tried by a special CBI court in Delhi, along with executives from some of India's best-known firms.
Lawyer-activist Prashant Bhushan, whose Public Interest Litigations have led to the Supreme Court monitoring the CBI's investigations in the telecom scandal, said that if the conversations are proved genuine, Mr Chandra's bail should be cancelled. Like Mr Raja, the Unitech MD spent many months in prison before being granted bail.