Iranian ministers should be punished if they deliberately failed to censor online content by “trouble-makers and enemies”, said the head of the country's cyber crime committee on Friday.

“The order to block all channels on encrypted messaging service Telegram, that in recent days incited the population to violence and trouble, was transmitted by judicial officials to the telecoms ministry a long time ago, but unfortunately nothing was done,” said Abdolsamad Khoramabadi, according to local media.

“If it is proven that officials voluntarily refused to take the necessary measures to prevent the activities of trouble-makers and enemies, they must be punished,” added Khoramabadi, who is also deputy to Iran's chief prosecutor.

Telegram and Instagram were blocked shortly after protests began on December 28, and officials also moved to shut down privacy software widely used to get round online restrictions. That marked a reversal for President Hassan Rouhani, who has pushed for online restrictions to be lifted as part of his efforts to improve civil liberties.

On December 19, he told the country's first conference on civil liberties: “We will not seek to filter social media. Our telecoms minister promises the people he will never touch the filtering button.”

At 36, Telecoms Minister Mohammad-Javad Azari Jahromi was the youngest-ever cabinet member when he was appointed in August, and has stated his opposition to internet controls.

They include bans on Facebook and Twitter, even though all the country's top officials, including the office of supreme leader Ayatollah Ali Khamenei, regularly tweet.

Instagram has been reinstated since the unrest calmed this week, but Jahromi said on Wednesday that Telegram could only return if it blocked “terrorist” content.

Khoramabadi claimed there were 8,500 channels on Telegram with content that was against “national security, the values of Islam and public morale”.

“The former minister and the current minister have resisted in the face of orders” to block these channels, he said. Rouhani has clashed with the conservative-dominated judiciary over his efforts to ease social regulations and release political prisoners.

“Unfortunately, certain people, either voluntarily or involuntarily, have assured the trouble-makers that no one will press the button of filtering to stop their illegal actions,” said Khoramabadi.

More than 41 million Iranians have smartphones in the country of 80 million, and at least 25 million use Telegram daily. For many it has become the main source of news and a way of bypassing Iran's highly restrictive media environment.