The licensor had earlier detected alleged misreporting of revenues by certain mobile service providers, even as it ordered inquiry into illegal long distance operations of certain multinational companies.

One of the main concerns of the licensor is that the ISP licence does not have clauses to deal with active infrastructure sharing among ISPs and national and international long distance (NLD and ILD) service providers, according to a source close to the development.

The DoT now wants a provision to be included in the ISP licence that will enable segregation of costs and revenues of various licences, he said.

The licensor's finance division will also "scrutinise" the calculations based on which ISPs report their adjusted gross revenues (AGRs). This will be mainly done for companies that have multiple licences and share infrastructure with telecom operators in the country, he said.

It would also issue guidelines to ISPs on reporting of revenues earned from usage of NLD networks, mainly from internet subscribers.

There are 164 ISPs in the country, with the top five being BSNL, Bharti Airtel, Reliance Communications, MTNL and Sify Technologies. The ISPs provide internet connectivity to around 13 million customers in the country, of which 5.65 million are broadband connections.

The government is planning to increase the broadband connectivity in the country to around 20 million by 2010. Earlier, the government had decided to undertake a special audit of telecom companies including Bharti Airtel, Vodafone Essar, Idea Cellular and Aircel over alleged mis-reporting of revenues.