The absence of a transparent telecom regulatory environment not only makes life difficult for service providers, but also impacts investors'' confidence in the sector, a senior Bharti Airtel official today said.

"We have lived through tough times, whether it was bidding for 3G licences or seeking clarification on whether roaming is possible or not and then receiving (getting to know) that it is questioned," Bharti Airtel CEO India and South Asia Sanjay Kapoor said at the 'National Telecom Summit 2011' organised by CII here.

"Not only does this make life more difficult for us, but also for investors, who don't feel confidence in our regulatory environment," he added.

Leading operators like Airtel, Vodafone and Idea had signed 3G roaming agreements for offering services in circles where they do not hold 3G spectrum.

This meant that if a user was in Kolkata on roaming and his/her service provider did not have a 3G licence in the circle, the user would still be able to access high-speed internet, thanks to the agreement.

The Department of Telecom is of the opinion that the agreement is in violation of licence rules and is examining the matter.

Operators have significant debt on their balance sheets, having paid huge sums for 3G and BWA spectrum in the auction last year, and any negative move might put the investments in jeopardy.

According to ratings agency Fitch, the outlook for bottom-rung telecom companies is negative in 2012 as they continue to suffer operating losses due to intense competition in the sector and lower ARPUs.

In contrast, the top four telcos are expected to record high single-digit revenue growth.

Kapoor, however, reposed confidence in the National Telecom Policy-2011.