The Bombay Stock Exchange said it had decided to exclude mobile operator Reliance Communications and power utility Reliance Infrastructure, both controlled by billionaire Anil Ambani, from the benchmark index.
The companies will be replaced by state-run Coal India, the world's largest coal miner, and leading drug maker Sun Pharmaceutical Industries in the Sensex, the exchange said in a statement on Friday.
The changes will be effective from August 8, the exchange said, without giving a reason for the move.
Reliance Communications, India's second-largest mobile operator, and Reliance Infrastructure are the two worst Sensex performers this year -- down 35 percent and 32 percent, respectively, while the main index has fallen 12 percent.
Shares in Coal India, in which the government sold a 10 percent stake last year for $3.4 billion in the country's largest ever IPO, are up 25 percent, while Sun Pharmaceutical shares have risen nearly 2 percent so far this year.