India lost up to $211 billion in revenue by selling coalfields too cheaply, a government auditor's draft report said, sparking a furore in parliament yesterday that added to pressure on the prime minister after months of scandals and policy missteps.

The prime minister's office called the estimated loss "exceedingly misleading," after the report, leaked from the federal auditor and published in the Times of India, prompted MPs to demand an explanation and rattled investors.

The auditor backed away from the loss calculation and said its thinking had changed.

Prime Minister Manmohan Singh, who oversaw the coal ministry during some of the period covered by the report, made no comment during his appearance in parliament.

He has lurched from crisis to crisis since massive graft in the sale of telecoms spectrum surfaced two years ago, culminating in the quashing of licences. The telecoms sale may have cost the government up to $36bn.

The uncertainty over coal contracts will add to investors' confusion about doing business in one of the world's fastest-growing economies.

The draft from the Comptroller and Auditor General's office criticised the allocation of 155 coalfields to about 100 private and some state-run firms between 2004 and 2009, questioning why they were not auctioned off to the highest bidder.

"This is the mother of all scams," said Venkaiah Naidu, a senior leader in the opposition Bharatiya Janata Party, which forced parliament to briefly adjourn over the report.