State-owned Indian Oil Corporation (IOC) said it will raise its stake in the joint venture building a 9 million tonnes refinery at Chennai to 75 per cent after the cost to the project escalated by over 12 per cent.

Originally, IOC and its subsidiary Chennai Petroleum Corporation Ltd (CPCL) were to hold a 25 per cent stake in the joint venture that was to build a new unit adjacent to the existing refinery of CPCL. The remaining 50 per cent equity was to come from financial investors.

In a stock exchange filing, IOC said its board at its meeting on Thursday "accorded approval for the revision in cost of the project from Rs 29,361 crore to Rs 33,023 crore".

"The Board has also accorded approval for revision in the capital structure of the joint venture with 75 per cent equity from IndianOil and 25 per cent equity from CPCL," it said.