Airtel, with a market share of 23.58 per cent and a customer base of 265.85 million, leads the market both in terms of revenue and customer base. With 204.68 million customers, Vodafone enjoys market share of 18.16 per cent. Idea has 16.9 per cent with 190.51 million customers as of December 2016, according to Trai data.

Today British telecom major Vodafone and Aditya Birla group-run Idea Cellular announced the merger of their operations, creating the largest mobile operator by customer and revenue market share.

Vodafone will own 45.1 per cent in the new company after transferring 4.9 per cent to the Aditya Birla group for Rs 3,874 crore in cash concurrent with completion of the merger. Idea will hold 26 per cent of the combined entity while the rest will be owned by public shareholders.

Idea and Vodafone said the merged entity will be jointly controlled by Vodafone and the Aditya Birla group as per shareholders' agreement.

According to CLSA report in January, the merged entity will have revenue of over Rs 80,000 crore, translating into a 43 per cent share by revenue and 40 per cent by active subscriber base with around 400 million customers.

The combined venture will account for over 25 per cent of the allocated spectrum and will have to sell about 1 per cent (worth Rs 5,400 crore) to comply with spectrum cap norms.

"The merger pegs implied enterprise valuation of Rs 82,800 crore (USD 12.4 billion) for Vodafone India and Rs 72,200 crore (USD 10.8 billion) for Idea," according to an exchange filing by Idea.

The companies had a net debt of Rs 1.07 trillion as of December 2016. Colao also said the merger makes possible synergies of USD 10 billion. He also added that both the brands, considering their strengths, will continue to operate separately.

Indicating Vodafone's intention of gradually exiting the country, Colao and Birla said over a period, both companies will have equal stakes in the merged entity.