Lack of confidence in the police response to the initial riots in London led to further disturbances across the country, an independent report has found.
The vast majority of people interviewed for a study of the causes of the disorder said they believed the "sole trigger" for disturbances in their areas was the perception that the police "could not contain" the scale of rioting in Tottenham, north London, and then across the capital in August.
"Lack of confidence in the police response to the initial riots encouraged people to test reactions in other areas," the Riots Communities and Victims Panel found.
"Most of the riots began with some trouble in retail areas with a critical mass of individuals and groups converging on an area.
"Rioters believed they would be able to loot and damage without being challenged by the police.
"In the hardest-hit areas, they were correct."
The findings were outlined in a series of recommendations in the interim report detailing the "sometimes horrifying and tragic" accounts of people's experiences of the disturbances.
The study found there was no one single motivating factor for the riots.
"We heard a range of motivations from the need for new trainers to a desire to attack society," it concluded.
In areas unaffected by the rioting, people felt that they too would have experienced the disorder had the disturbances in other areas had continued for much longer, the report found.
"Few people ruled out the prospect of riots in the future," it added.
The report authors said they had heard "harrowing" stories on visits to areas affected by rioting.
"Lives were lost. Parents had to carry children out of burning homes, leaving a lifetime of possessions behind to be destroyed," it said.
"Shopkeepers lost everything they had built up over many years. The consequences of the riots are still being felt.
"In many areas, there is an overriding sense of despair that people could destroy their own communities."
The report's recommendations included an overhaul of the 1886 Riot Damages Act to ensure that victims of the riots receive compensation quickly.
The panel had not heard from anyone who had received a payment under the Act, with forecasts that by March next year "barely half" of the smallest and only one in 10 of the largest claims will have been paid.
The report also called for the insurance industry to tackle cases where service has been poor following complaints about the speed of insurers and the treatment of claimants.
Local authorities and emergency services should review procedures for helping and evacuating residents and bystanders caught up in riot areas including through designated "safe havens", the report found.
Police authorities should "immediately" review their emergency plans to ensure they properly cover public disorder on the scale of the August riots, the panel found.
Darra Singh, chairman of the panel, said in a news conference that the riots could happen again if immediate action was not taken.
"Our findings support the view that had the police response in Tottenham and more widely in London been more robust, the riots would not have spread elsewhere in England," he said.
"Our research has also led us to conclude that riots of this nature will happen again unless immediate action is taken," he said.
The report said the panel estimated that between 13,000 and 15,000 people were "actively involved" in the riots between August 6 and August 10.
More than 4,000 suspected rioters have been arrested with nine out of 10 already known to the police, the study said.
More than 5,000 crimes were committed, including five fatalities, 1,860 incidents of arson and criminal damage, 1,649 burglaries, 141 incidents of disorder and 366 incidents of violence against the person.
The final bill could be around £500 million, with up to £300 million of claims under the Riot Damages Act and £50 million on policing London.
The report recommended that following the shooting of Mark Duggan in Tottenham, north London, the Independent Police Complaints Commission (IPCC) and the police "urgently" review existing protocols and ensure they are followed in the future.
The riots, which began in Tottenham, spread across the country with "unprecedented" speed, the panel found.
"In our view they were triggered by the police handling of the death of Mark Duggan, in particular communication with his family, which was caused by the breakdown of their protocols with the IPCC," the report noted.
The report also said stop and search needed "immediate attention" to ensure community confidence was not undermined.
This followed complaints from many people that police stop and search was "consistently" carried out without courtesy.
Victims should be able to confront rioters who committed crimes against them, the report said, and service personnel who protected communities at "great risk" should be honoured.
There should also be a fund to support struggling high streets as footfall remains "seriously down" in some riot hit areas, it said.
There should also be "clear plans" to help cut the risk of re-offending by convicted rioters, the report added.
Panel member Heather Rabbatts told the news conference the Duggan case was "clearly" a catalyst for the riots in Tottenham.
"They then changed in character and we consider in the report how the contagion was spread," she added.
"There were large scale incidences of opportunistic looting.
"These were not riots that were political, these were particularly characterised by opportunistic looting and very much targeted at brands."
She added: "The latest brand or gadget increasingly defines all of our sense of identity."
Ms Rabbatts said one of the "recurring themes" was the issue of stop and search which was cited as a "tension" between communities and the police.
Mr Singh said: "In many areas people felt abandoned by public servicemen, by the police and therefore we want to ask police in particular to be sure that we are clear in future about the balance between protection of commercial property versus protection of residential areas and of individuals in their own homes."