Telecoms Licence Row
Comptroller and Auditor General of India (CAG), an official watchdog, said in a report this month that the telecoms ministry gave lucrative licences and spectrum at below-market prices, depriving the government of up to $39 billion in revenues.
The auditor also said several rules were flouted when the licences were given out in 2007/08, which led to many ineligible firms getting licences.
While nobody has been charged yet, investigations have focused on the telecoms ministry, firms and lobbyists.
Telecoms minister Andimuthu Raja was ordered by the government to resign after the report was released.
Raja has denied any wrongdoing. The CBI has also launched an investigation into alleged corruption at the ministry.
The CAG report says units of realtor Unitech were given licences despite not having adequate capital. The units are now part of the India operations of Norway's Telenor.
Swan Telecom, which has since been bought into by UAE's Etisalat, was given a licence despite being disqualified as No 2 telecoms firm Reliance Communications owned more than 10 percent in it, the auditor said.
Reliance Communications was also given undue benefits as it sought permission to offer services under the more popular GSM technology, the auditor said.
All firms have denied wrongdoing and have said they complied with all rules when licences were given.
Authorities have questioned Nira Radia, a top lobbyist who represents companies like Tata and Reliance Industries, as part of an investigation into whether money laundering and forex laws were broken when the licences were purchased.
Prime Minister Manmohan Singh has been criticised for sitting on a request to grant permission to charge Raja with corruption and been forced to answer questions from the Supreme Court.