The Chief Constable of Greater Manchester Police has accused colleagues in London of failing to respond fast enough to prevent copycat violence spreading during this summer's riots.
Peter Fahy said: "A certain group of people saw what was happening in London and decided they seemed to be getting away with it."
Manchester and neighbouring Salford saw some of the worst disturbances three days after it began in the capital.
Greater Manchester Police have arrested more than 350 people in connection with the trouble while detectives are still working to track down hundreds more suspects.
Mr Fahy, who said he did not regret sending 100 of his officers to the capital to help, told BBC Panorama: "I think you'd have to say with hindsight if London had been under control sooner we probably would not have faced the problems in Manchester."
Scotland Yard declined to comment but Paul McKeever, chairman of the Police Federation of England and Wales, said: "Peter Fahy is a man who is held in high regard and respect and somebody we should listen to, but the officers in London did a magnificent job, putting their lives on the line to protect their communities."Reuse content