The stock opened at 755 rupees, compared with its initial public offering price of 570 rupees. Analysts had expected the stock to list at a premium of 10% to 15%.

The benchmark index Nifty 50 was down 0.4%, while shares of Bharti Airtel, India's No.2 telecom operator by subscribers, were down 0.6%.

The billionaire Sunil Mittal-led Bharti Airtel owns 70% of Bharti Hexacom, which is the latest unit of a conglomerate to cash into investor appetite for public offerings as the stocks market hits record highs.

The Tata Group's Tata Technologies and JSW Group's JSW Infrastructure had strong debuts late last year.

So far this year, 64 Indian companies have gone public, raising $2.31 billion cumulatively, compared with 42 companies raising $170.6 million in the same period last year, according to LSEG data.

Bankers expect the momentum to persist amid rapid economic growth and expectations of political stability.

While Bharti Airtel operates across India, Bharti Hexacom offers mobile, broadband and fixed-line telephone services under the "Airtel" brand in the northwestern state of Rajasthan and some parts of northeastern India.

The 42.75-billion rupee IPO was oversubscribed 29.88 times last week. Government-owned Telecommunications Consultants India sold half of its 30% stake in Bharti Hexacom in the IPO. The company itself did not issue fresh shares.

($1 = 83.3750 Indian rupees)

(Reporting by Rama Venkat in Bengaluru; Editing by Sonia Cheema)