The new rules, called The Telecom Commercial Communications Customer Preference Regulations 2010, were to come into effect in January this year, but their enforcement was postponed because of a delay by India's Department of Telecommunications in allocating a separate numbering scheme for telemarketers.

The country's security agencies are said to have objected to prefixing telemarketer telephone numbers with a single "140" sequence across the country, as it would make it difficult to trace calls. Currently calls can be traced to their original location in the country and the carrier by the sequence of numbers.

India introduced a do-not-call registry in June 2007 but three years later it was found that it did not meet the requirement, because telemarketers had shifted from voice calls to SMS (Short Message Service). A large number of subscribers did not enroll in the registry because they found the procedures tedious, Telecom Regulatory Authority of India (TRAI) said.

TRAI has now introduced stiffer penalties for telemarketers, designed to prevent both unsolicited telemarketing calls and SMS. Service providers have also been made responsible for unsolicited telemarketing calls and SMS that originate from their networks.

A boom in India's economy has seen a surge in telemarketers offering a variety of services ranging from finance and insurance to real-estate and holiday packages.