Terming unsolicited calls more intrusive than SMSes, Tata teleservices today said operators should be made to pay more penalty for such voice calls than for sending spam messages.

"...SPAM calls and SMS should be differentiated so that call nuisance be addressed more than text e-mail and SMS spam," TTSL said in a statement adding that there should 10 times more severe penalty for intrusive voice calls than SMS spam messages.

TTSL's comments on unsolicited calls comes at a time, when the Supreme Court had issued notices to telecom operator Bharti Airtel and private banks ICICI bank and American Express over unsolicited calls to mobile phones.

Bharti Airtel, however, had recently said that they are moving out from the business of bulk SMSes.

Stating that e-mails and text intrusion, are far more acceptable than telemarketing voice, TTSL said in case of SMSes the "degree of disturbance is far lower".

"Many telecom operators are permitting unsolicited calls by telemarketers and by their very nature, these calls are intrusive and a violation of the personal space of subscribers," TTSL's Chief Technology Officer AG Rao said.

This comes in the backdrop of Telecom Minister A Raja ordering action to stop unsolicited calls by telemarketing companies.

The issue surfaced after Finance Minister Pranab Mukherjee received a call from a telemarketer when he was in an important meeting with the Opposition parties.

TRAI had already floated a consultation paper on curbing such commercial calls and messages in May this year.