Prime Minister Manmohan Singh has come under pressure to step down over India’s troubled coal sector ahead of elections in 2014, AFP reports.

According to the Asahi Shimbun, the Central Bureau of Investigation is investigating “under the table” deals between state officials and private companies, causing uproar in parliament. The underpriced sales of coal concessions cost the exchequer as much as $33 billion in lost revenues, according to state auditor’s estimate. The government has awarded a net total of 195 blocks, with reserves of 44.23 billions tons, reports the Asahi Shimbun. As of March, only 28 were operating with an output of just 38 million tons a year. The gap between demand and supply is a setback to the coal-dependent third-largest economy in Asia.

Prime Minister Singh was coal minister between 2006-2009, when most of the sales occurred. Tensions over the corruption scandal paralyzed the parliament for two days. Ravi Shankar Prasad, deputy leader of the Bharatiya Janata Party in the upper house, accused Singh of being involved in the “coalgate” affair and demanded him to resign, which was echoed by opposition lawmakers. Singh denied the allegations and vowed that he would only resign “if it is proven that he acted inappropriately as coal minister”. This comes as the Congress-led government seeks to revive political clout.