"We arrested 300 people [in Salford and Manchester] and we sent a powerful message, but a lot of people on the periphery got away with it.
"Probably, if I was them, I'd have thought: yeah, I'd do it again, and probably get away with it next time."
Officers from eight forces deployed in London, Birmingham, Liverpool, Manchester and Salford were interviewed for the second part of Reading the Riots, a joint study by the Guardian and the London School of Economics.
Their accounts are published as rank-and-file police are involved in a bitter dispute with Home Secretary Theresa May over budget cuts.
Police acknowledged that forces were stretched to the limit by the speed and the scale of the violence and looting, and in places were totally overwhelmed.
Senior officers in London accepted that they struggled to deploy enough manpower to contain the disorder during the four days of unrest in the capital.
The report found that the Metropolitan Police did not activate a national alarm system to call for more resources until day three - and once other officers from outside forces did arrive, they were hampered by poor communications with central command.
It also suggested forces across England were wrong-footed by the use of social media networks, particularly encrypted Blackberry messaging, to enable rioters and looters to organise.
Paul McKeever, chairman of the Police Federation, said the Government must take "urgent stock" of the report.
He said: "Officers interviewed rightly identify and voice concern that, should the same circumstances occur again, the police service would struggle to cope and contain the situation with the loss of police officers' numbers we are experiencing as a direct result of the cuts - over 5,000 last year alone."
The Met said that since the riots it had adapted its tactics, given more training to officers and procured new technology for monitoring social media.