By Michael Holden

LONDON (Reuters) - U.S. "supercop" Bill Bratton, visiting Britain to advise the government in the aftermath of riots earlier this year, said on Tuesday he was against the idea of shutting down social media services during times of civil unrest.

Police and politicians said rioters and looters had coordinated their actions and used services such as BlackBerry Messenger and Twitter to incite trouble during the large-scale disorder which swept Britain in August.

Prime Minister David Cameron said at the time Britain might consider disrupting online social networking during any future trouble, and senior figures from Twitter and Research in Motion, which owns Blackberry, were summoned by politicians last month to discuss the issue.

However Bratton, former police chief in New York, Los Angeles and Boston, where he oversaw dramatic falls in street crimes gaining him the "supercop" moniker, cautioned against such a move, saying it would badly impact on "good people."

"You have the potential to throw the whole community into even more critical shock," he told a British parliamentary committee, referring to his own experiences of trying to contact family in the aftermath of the September 11 attacks.

He said social networking also helped the authorities warn people about where disturbances were occurring, while the police themselves often relied on the likes of Blackberry.

"There's no denying in policing ... that we are attempting to play catch up with (technology's) impact," he said.

Bratton is due to meet Prime Minister David Cameron and Home Secretary (interior minister) Theresa May during his UK visit, as well as attend a high-level conference on gangs to pass on his knowledge of helping to quell gang violence in Los Angeles.

Cameron has blamed much of August's rioting, the worst in Britain for decades, on street gangs.

NASCENT GANG PROBLEM

Bratton, now chairman of Manhattan-based risk consultancy firm Kroll, said Britain had a "nascent" problem with street gangs compared with the situation he inherited in Los Angeles where there had been some 100,000 gang members and more entrenched violence.

"The approach to gangs is they will always be in existence," he said. "What you can do is control their behavior and seek to prevent their expansion."

He said the key was to stop young people being recruited or coerced into joining gangs, and that it was vital police worked in partnership with local communities and agencies to offer young people an alternative.

The decision to call on Bratton for advice was greeted with skepticism and outright hostility by some senior British police, officers smarting over criticism of their handling of the riots.

However, such is Bratton's standing that Cameron had hinted that he had wanted him to be London's next police chief when the position became vacant over the summer.

The American was ruled out when May said the new commissioner had to be British because of national security issues.

Asked if he was disappointed not to have been the London chief, a smiling Bratton told the committee: "It's water under the bridge" before ruling himself out of any jobs in British policing.

(Editing by Maria Golovnina)