Jio had already left Bharti Airtel behind in May to become the second largest mobile operator with 322.9 million users and 27.80 per cent market, according to Trai data. Airtel had 320.38 users or 27.6 per cent market share.
Vodafone said: "Our subscriber base declined to 320.0 million from 334.1 million in fourth quarter of financial year 2019 primarily due to customer churn following the introduction of ‘service validity vouchers' in the prior quarters."
At the time of merger, Vodafone Idea had emerged as the largest telecom operator with over 400 million subscribers.
However, Jio has left all rivals behind with its cheaper, fast and accessible offers.