Cleric Ayatollah Ahmad Jannati made the call during Friday prayers in Tehran. He was speaking against a background of an intensified power struggle between Iran's conservative faction and the moderates.

Since reformist President Mohammad Khatami came to power 18 months ago, the Iranian press has become freer and more colourful than at any time since the Islamic revolution.

The Internet is also increasingly in demand with youngsters keen for information on the latest American movies and music, although it currently does not have the kind of reach it has in the West.

Many moderates are in favour using the positive side of satellite channels and the Internet, but Iran's conservative religious leaders are afraid they could end up losing the hearts and minds of the country's young people.

Ali Mohammadi of Nottingham Trent University in England says the information revolution is bypassing traditionalists.

"If the Internet provides masses of various information channels to the young people, then they won't have to go to the traditional religious leaders to seek advice," he says.

However the information revolution is slowed by Iran's strict Islamic laws, which mean Internet service providers have to operate a form of self-censorship.

Said Vahid, an employee of Nedanet, a Tehran Internet provider service, says software is used to screen out some sites.

"Some adult sites are blocked and users can't access those sites and some sites of dissident Iranian groups and some religious sites are also on the black list," he says.

Iranian TV 'boring'

Iran's conservative dominated state radio and television is also losing younger viewers. Dr Mohammadi says Iranian TV is seen as boring.

"People are looking for fun, for some entertainment and this is why they would rather look to radio and foreign television," he says.

"They make tapes to give to those who haven't got the money to have their own satellite television," he adds.

The viewing of satellite television has tripled since President Khatami came to power, largely because he has not actively enforced an existing ban on owning satellite dishes, Dr Mohammadi says.

Ayatollah Jannati called for Iran's existing media to try to win back viewers by producing more attractive programmes on the life of the prophet Mohammad and the early history of Islam.