The decision comes after the unanimous view of telecom regulator Trai, Law Ministry and DoT that such roaming agreement was in violation of the telecom licences.
Leading operators like Bharti, Vodafone and Idea had entered into agreement with one another to offer 3G mobile services in circles in which they could not succeed in getting spectrum in the auction held last year.
"The decision has been taken that this (3G roaming pacts) is in violation of terms and conditions of the licence... will be issuing notices asking them (operators) to stop their service with immediate effect. But on penalty, no decision has been taken yet," Telecom Secretary R Chandrasekhar told PTI.
The issue pertains to the pact among major service providers, including Bharti Airtel, Vodafone Essar and Idea Cellular, for providing 3G roaming network on a pan-India basis.
Other service providers like Tata Teleservices and Aircel had also entered into similar agreements to offer services in six circles. However, they have already discontinued the arrangement.
The Department of Telecom (DoT) had sought a legal opinion on this matter and the Law Ministry had supported the DoT's view.
In an internal note, the DoT had said the roaming agreement among telecom companies for 3G services would lead to a significant loss of revenue to the government.