Coal supplied by Coal India Ltd (CIL) is becoming costlier than its equivalent imported version as global prices are declining.

A senior official from a West Bengal-based power company said that they found all categories of CIL coal costlier, when they took in account the actual quality of coal supplied by the government-owned coal miner.

Speaking on the condition of anonymity, the official said, "For certain grades, CIL's coal is in fact turning out to be costlier than its equivalent imported version because of grade slippage and stones that come mixed with the coal."

A senior official from NTPC also had a similar complaint. He said that there were big amount of stone in CIL coal that made it really hard for us to find grounds to dispose those stones off.

Coal from CIL is also turning out to be costlier due to decline in the global prices of low-quality coal. The gap between coals from CIL and Indonesian has slipped from 30-40 per cent around a year ago to just 15 per cent now.

The remaining gap of 15 per cent is only due to the transport cost that Indian power companies have to pay to import coal from Indonesian mines. In case CIL hikes prices of its coal, the gap may vanish altogether.

When contacted, CIL chairman S Narsing Rao claimed that he was not aware of the global prices of coal. However, he admitted that sometimes stones were supplied with coal to power plants that led to quality issues.