Ministers and the security services are planning draconian powers to shut down or disrupt mobile phone messaging services and social networks in times of civil disorder.
The warning came as police “fightback” raids mounted against riot and looting suspects yesterday.
Downing Street sources said they were considering the “moral and technical” questions of how to grant new powers blocking all mobile communications to prevent rioters organising through websites such as Twitter and the BlackBerry Messenger service.
Prime Minister David Cameron, (below) said “nothing should be off the table” in efforts to prevent a repeat of this week's rioting in London and other English cities.
The new powers prompted politicians, social media companies and civil liberties campaigners to warn against a “knee-jerk” response which could infringe the freedom of expression and business of law-abiding web users.
Privately, senior police officers also expressed doubt that the measure would have anything more than a “marginal effect” on preventing disorder and said the real issue was the numbers of officers on the streets.
The president of the Association of Chief Police Officers, Sir Hugh Orde, has also warned that “to suggest human rights get in the way of effective policing is simply wrong”.
But Mr Cameron, promising yesterday to do “whatever it takes” to restore order, outlined a series of new security measures which included further powers of curfew, looking at using the Army to free up police for “frontline” duties, giving police officers the power to force people to remove scarves, hoods or masks covering their faces or be arrested and extending “gang injunctions” banning teenagers as well as adults from associating with each other or visiting designated areas.
The Government will also consult former New York Police commissioner Bill Bratton on further measures to tackle gang culture.
Mr Cameron confirmed that a Parliamentary debate would be held on whether convicted looters should lose their benefits after more than 100,00 people had signed an e-petition calling for it.
His comments on censoring or shutting down social media sites and mobile networks are likely to prove controversial.
“Free flow of information can be used for good, but it can also be used for ill,” he said.
Social media expert Graham Cluley said: “Although the Prime Minister's motivation might be sincere, he's not going to be able to stop people from communicating via the likes of Facebook and Twitter. There's plenty of unpleasant, hateful and illegal activity going on via these sites already.
A spokesman for the civil liberties group Big Brother Watch said: “The fact that this is even being considered should send a chill wind through the whole country.”
As the debate over how to deal with any future events continued, suspects wanted over violence were being raided throughout the day as the police fightback began.
Designer clothes worth thousands of pounds were recovered from one flat alone as the first of hundreds of expected raids began.
Intelligence-led swoops by 50 officers followed violent scenes in Sloane Square on Monday, where up to a million pounds worth of damage was caused.
A Hugo Boss shop was the target of about 40 looters who emptied the store of its contents on Tuesday.
In response, four arrests were made yesterday as suspects were dragged from their homes during searches in Pimlico, central London.
One 18-year-old man screamed at officers as he was bundled into a police van in handcuffs after more than £1,000 worth of clothing was found in his flat.
Brand new Nike Air Jordan trainers, along with Hugo Boss jackets, jeans, belts and bags were taken away from his flat.
Many of the looters will also face eviction from council homes if they are convicted.
Another eight homes in Lambeth were raided. Officers made a number of arrests during simultaneous searched in Brixton.
Deputy Assistant Commissioner Steve Kavanagh said Scotland Yard is in the process of “working through” more than 100 warrants.
Last night Scotland Yard said a total of 950 people had been arrested in connection with violence, disorder and looting in London since Saturday, of whom 457 have been charged.