Prime Minister David Cameron said on Thursday that government was considering blocking the use of social media services like FaceBook, Twitter, BlackBerry Messenger to prevent riots.

The services were widely used by rioters during the four days of violent looting and vandalism across London. Theresa May, the Home Secretary would meet with executives of the social media companies FaceBook and Twitter as well as BlackBerry manufacturers, Research in Motion to discuss possible measures that could be put in place.

"Everyone watching these horrific actions will be struck by how they were organized via social media," Cameron told Parliament during a special debate on the riots. "Free flow of information can be used for good. But it can also be used for ill.

"And when people are using social media for violence we need to stop them. So we are working with the police, the intelligence services and industry to look at whether it would be right to stop people communicating via these Web sites and services when we know they are plotting violence, disorder and criminality."

Cameron did not specify whether the proposed plans would include blocking individuals from using the sites or shutting down access to the sites in affected areas.

The proposal met with opposition from free-speech groups and social media and legal experts. Any move to curb social media use would be difficult to enforce and could violate basic freedoms.

"It seems like a bizarre and kind of knee-jerk reaction by the government," said Padraig Reidy, news editor of Index on Censorship. "We've seen this kind of thing time and time again, especially with young people, when it comes to technology. Now it's social networks and smartphones. A few years ago it was video games. Before that it was horror films."

Podraig compared the move to Egypt government's denying access to the Internet and mobile phone networks during the massive protests against Egypt's President Mubarak.

"Just because you can do it doesn't mean you should. These things weren't caused by Twitter or BlackBerry."

RIM has released the same response to the Prime Minister's remarks.

"As in all markets around the world where BlackBerry is available, we cooperate with local telecommunications operators, law enforcement and regulatory officials. Similar to other technology providers in the U.K. we comply with the Regulation of Investigatory Powers Act and co-operate fully with the Home Office and U.K. police forces."

Twitter has not released any response; FaceBook meanwhile said it had removed "credible threats of violence" from the site as well as accounts that were registered under fake names.

"We look forward to meeting with the home secretary to explain the measures we have been taking to ensure that FaceBook is a safe and positive platform for people in the U.K. at this challenging time," the company said.