The Supreme Court (SC) of India on Monday issued notice to Union Communications Minister A Raja, the CBI and DoT to reply to a petition alleging that the CBI was going slow with its investigations into alleged 2G spectrum allocation.

Centre for Public Interest Litigation's (CPIL) lawyer Prashant Bhushan asked the court to direct the CBI to produce the records of the case that involves the alleged irregularities in allocating 2G spectrum to new and dual tech players in 2007.

The CPIL petition challenged an earlier verdict of the Delhi High Court which dismissed its plea for the court to monitor the investigation.

The SC has given 10 days time to A Raja, DoT and CBI for responding.

During the hearing, Bhushan read out letters exchanged between the CBI and income-tax department regarding taped conversations between chairman of PR firm Vaishnavi, Niira Radia, Raja and DoT officials. He said telephone call records showed how middlemen regularly interacted with officials and influenced policy-decisions and grant of licences.

"If they have heard the conversation, why do they say might have had. Why is there so much of uncertainty?" the bench asked.

The court also took exception to CBI's FIR registered against "unknown persons." It noted: "Why is CBI so uncertain? Doesn't the CBI know the officials involved?"