India's opposition Bharatiya Janata Party (BJP) Friday urged Prime Minister Manmohan Singh to resign over a huge economic loss resulting from alleged mismanaged coal block allocation.

The Indian exchequer could have earned 185 billion rupees (37 billion U.S. dollars) more if a competitive bidding process was followed in the award of coal blocks to private and government players, the official auditor said in its report released Friday.

The BJP held Singh directly responsible as he held the Coal Ministry portfolio when the loss allegedly occurred.

The Comptroller and Auditor General of India said the losses occurred because the process of bringing transparency in the award of coal blocks, which was to commence in June 2004, got delayed due to various reasons.

The BJP has stepped up attack on the government over various issues as the 2014 general election comes within agendas of India' s political parties.

A latest public opinion poll by the India Today magazine published on Friday said the BJP is surpassing the Congress-led United Progressive Alliance (UPA) in support rate, because of increasing discontent over high inflation, corruption and unemployment under the UPA rule since 2004.