Business Standard reports Bhattacharya has called for the estimate to be "pruned down" to a more realistic estimate.

Current estimates reveal the country has a total coal reserve of 222 billion tonnes from proven, indicated and inferred resources.

Bhattacharya told Business Standard that when the unmineable reserves are deducted from the country's total, India could run out of coal within 40 - 45 years.

For this reason he said Coal India was trying to secure coal supplies in other countries, namely Australia, Canada and Mozambique.