Telecom regulator TRAI has asked leading telecom service providers, including Bharti airtel, Vodafone and Idea, to justify their decision to hike mobile tariffs by up to 20%.

"We have sent letters to all the companies which have recently hiked tariffs seeking justifications for the reasons as to why they have hiked the tariffs and the reasons for the same. The last one (letter) gone to Reliance Communications," TRAI chairman JS Sarma said on the sidelines of an event.

Recently, companies like Bharti airtel, Idea Cellular, Vodafone and Reliance Communications raised tariffs for their services by about 20% in most operating circles.

Most of the companies cited inflationary pressure in the country as being responsible for the tariff hike. Airtel had raised the tariffs for its ''Advantage' and 'Freedom' pre-paid tariff packages, which are based on per minute billing, to 60 paise per minute for local and STD mobile-to-mobile calls. Earlier, it was 50 paise per minute in this category.

"Telecom is probably the only industry where, despite increasing inflation, tariffs have been falling unabated. Continuously declining margins, high 3G and BWA auction prices, constrained spectrum and rural roll-out aspirations leave us with little choice but to make some price corrections," Bharti airtel had said in a statement.