The makers of BlackBerry admitted today social media could be used for "malicious purposes" but the vast majority of users were law-abiding, during a grilling by British lawmakers on August's riots.

Stephen Bates, managing director of Research in Motion in Britain and Ireland, insisted that social media was generally a "force for good", a position backed by executives from Facebook and Twitter during the hearing in London.

"There's no dispute that... social media was used for malicious purposes," Bates told parliament's home affairs committee, which is conducting an inquiry into the four nights of unprecedented riots in English cities.

Commentators have dubbed them the "BlackBerry riots" because they were fuelled by the use of BlackBerry Messenger (BBM), an instant messenger service on phones which can be shared between up to 30 people.

Bates acknowledged that "BlackBerry is the mobile phone choice of the youth of Britain" but said the majority of its seven million British users, who included many police officers and workers at top companies, were law-abiding.

The committee also quizzed Richard Allan, the director of policy for Facebook, and Alexander Macgillivray, general counsel responsible for public policy at Twitter, who flew in from California for the hearing.

The MPs heard that both BlackBerry and Facebook had received requests from the police for information about the riots, but no details were given.

Media watchdog Reporters Without Borders criticised the Canada-based Research in Motion last month for helping police identify rioters who used BBM, citing privacy concerns.

Bates refused to disclose in public whether BlackBerry messages had been handed over to the authorities, saying only: "Whenever there is a legitimate response from the police we will respond to it."

Both Allan and Macgillivray meanwhile told MPs that Facebook and Twitter were too open to be of much use to criminals, and said they had found little evidence that they played a part in encouraging the rioters.