A media watchdog voiced concern Saturday at the cooperation between British authorities and the Canadian maker of BlackBerry smartphones to identify rioters in London and other cities.
"What consequences will this cooperation have on respect for the privacy of BlackBerry users?" the Paris-based Reporters Without Borders said in a statement.
If information provided by BlackBerry-maker Research in Motion (RIM) leads to arrests, "questions will be raised about the validity of the evidence and the legality of the way it was acquired," the lobby group continued.
Reporters Without Borders stressed that it was not minimizing the gravity of the situation in Britain and the urgent need to restore order, but added that the provision of personal data to the police sets a "disturbing precedent" coming from a western nation which could have consequences as regards "setting an example for others kinds of government."
There were nights of rioting, looting and arson in several major English cities this week, sparked by a police shooting in Tottenham, north London, where the trouble began last Saturday.
There have been three quieter days following four nights of mayhem which have led to 1,600 arrests across the country.
The rioters and looters were able to organise rapidly through text messages which, using the BlackBerry system, are encrypted unlike such online social network sites as Twitter.
Reporters Without Borders expressed shocked at suggestions by several politicians that BlackBerry suspends its messaging service and urged the British authorities "to rule out any possibility of shutting down or drastically restricting the use of social networks such as Facebook and Twitter."
David Lammy, the opposition lawmaker for Tottenham on Tuesday said the messaging service was "one of the reasons why unsophisticated criminals are outfoxing an otherwise sophisticated police force."
The group also voiced concern at Prime Minister David Camerons suggestion that TV broadcasters have a duty to hand over unused footage of the rioting to the police.
"This would turn them into police auxiliaries and seriously endanger their independence," the statement argued.
RIM has been pressured by governments in the past and has yielded to ultimatums from repressive regimes in countries such as United Arab Emirates and Saudi Arabia for the filtering of websites, access to user data, or the censorship of encrypted services, the group added.
Patrick Spence, managing director of global sales and regional marketing for BlackBerry, has publicly announced that his company is cooperating with British police.
"We feel for those impacted by recent days' riots in London. We have engaged with the authorities to assist in any way we can," he said.
The BlackBerry messenger (BBM) uses the internet rather than the mobile phone network and requires user authentication, which makes it hard for the authorities to intercept messages.
To help address this difficulty, the group said, RIM has already provided Scotland Yard with information about a number of BlackBerry users, jeopardizing their personal data.
Although BlackBerrys are normally associated with white-collar workers keeping up with their emails, they are used by 37 percent of young adults and children in Britain, according to recent industry figures.
Explore further: Net expansion driven by mobile presents risks and opportunities for marketers