The opposition today mounted a concerted attack on the government over allegations that union law minister Ashwani Kumar and senior officials in the Prime Minister's Office may have reviewed and altered a report submitted by the Central Bureau of Investigation to the Supreme Court on how coal fields were allocated to private firms between 2006 and 2009.
The Supreme Court had earlier asked the CBI director to state in writing that the report had not been shared with "the political executive".
The Bharatiya Janata Party is demanding that the "original and unaltered" report prepared by the CBI be made public and the investigation be handed over to a Special Investigation Team (SIT).
"This is evidence of the government's pressure on the CBI to save the Prime Minister," BJP leader Sushma Swaraj tweeted.
Arun Jaitley of the BJP also demanded constitution of a SIT, accusing the United Progressive Alliance of being a "rogue government" that will not allow CBI to function independently.
Jaitley, the leader of the opposition in the Rajya Sabha, also charged the government with "interference in the administration of justice" by not allowing CBI to acquaint the apex court with the full truth.
The charges that law minister Ashwani Kumar met CBI director Ranjit Sinha and asked for changes to the CBI's status report was given to the Supreme Court were detailed in the Indian Express newspaper.
The Congress has rejected the charge of interference in the preparation of CBI report on the coal scam for the Supreme Court and ruled out resignation of Kumar over the issue.
"There is no question of resignation of law minister Ashwani Kumar. Supreme Court has already asked CBI to file an affidavit in this regard. CBI will file its affidavit and truth will come out,'' party spokesman Rashid Alvi said.
"The matter is being investigated under the supervision of the Supreme Court. The BJP should wait and not try to misguide the country and not try to create obstacles in the way of investigations."
The government was first hit by the 'coalgate' scandal when the Comptroller & Auditor General of India said in March 2012 that the country lost Rs1,86,000 crore because coalfields were allocated without a transparent bidding process.
The government argues that its policy was not focused on revenue, but on ensuring industrial and infrastructural development.