New Delhi, Nov 17 (IANS) The Communist Party of India-Marxist (CPI-M) Wednesday asked Prime Minister Manmohan Singh to explain how the "murky" 2G spectrum scam dragged on and sought the prosecution of disgraced former communication minister A. Raja.

"The Supreme Court has correctly asked why the prime minister delayed responding to the request for permission to prosecute the (former) telecom minister for 11 months?," it said in a statement.

"It should be further asked why the prime minister refused to order a probe on the telecom scam for a longer period despite repeated requests.

"For instance, the CPI-M leader in the Rajya Sabha, Sitaram Yechury, had written to the prime minister in November 2008 asking for an enquiry.

"The prime minister should explain in parliament how this murky affair was allowed to go on for so long," it said.

The statement pointed out taht the report from the Comptroller and Auditor General on the issue of licenses and allocation of 2G spectrum had confirmed what has been in public knowledge for long.

"That the government suffered a loss of revenue amounting to Rs. 1.76 lakh crore makes the telecom scam the biggest corruption case.

"Not only Raja along with other guilty officials be prosecuted, but immediate steps should be taken to undo the damage and recover the lost revenue.

"All the companies who have benefited illegally should be asked to pay up the full amount as per the market value of the spectrum allocation.

"Further, companies who got the licenses and spectrum allocation illegally and by violation of the norms, their licenses should be cancelled.

"Corporate crime cannot be condoned as the UPA (United Progressive Alliance) government is prone to do so."