Bharti, whose tie-up talks with South Africa's MTN collapsed last month for a second time, denying it access to vast new markets and revenue streams, is facing tremendous competition at home.
Four new firms, including ventures of Telenor and Etisalat, are set to start operations this year and existing firms are scrambling to sign up users before then by drastically dropping call charges.
"There is clearly more pain left in the sector as competitive pressure is expected to intensify in the months ahead," said R.K. Gupta, managing director of Taurus Mutual Fund, which holds Bharti stock.
"Margins of these mobile companies will remain under pressure for some time. I don't think anyone should think of taking fresh exposure in telecom stocks at this point in time."
Shares in Bharti, India's seventh-most valuable firm with a market value of about $25 billion, fell as much as 6.9 percent to its lowest in seven months.
By 0800 GMT, the stock was down 5.4 percent at 295.10 rupees in a firm Mumbai market, with 4.7 million shares changing hands, more than two-and-a-half times the 90-day average.
Bharti, which has more than 23 percent of India's 470 million-plus mobile subscribers, will be forced to match rivals' prices to retain its market share, but any such move would mean sacrificing revenue and earnings growth, analysts say.
