Toronto police failed to stop a riot during the G20 summit two years ago because they were so focused on guarding the security fence around the site of the meeting, a new report says. And when Chief Bill Blair's officers asked the RCMP to relieve them at the perimeter so they could deal with the vandalism in the streets, it took a full 12 hours for the federal police force to do so.

The review, conducted for the civilian board that oversees the Toronto Police Service by John Morden, former associate chief justice of Ontario, was to be released on Friday morning.

Problems with the security operation began months before the summit, Mr. Morden found, because the federal government chose a location for the gathering – the Metro convention centre in downtown Toronto – so late that police did not have enough time to prepare.

Story continues below advertisement

Such a large security operation typically takes two years to plan, Mr. Morden wrote. Toronto police, however, had four months.

The report also takes the civilian board to task for not reviewing the force's plans. On one occasion, Mr. Morden wrote, the chair dismissed a question from a board member about the guidelines for using a sound cannon.

Chief Blair and board chair Alok Mukherjee will discuss the report on Friday. Public Safety, the federal department that oversees the RCMP, did not immediately comment.

During the summit, RCMP was responsible for security at the site of the meeting. The surrounding fence – called the "interdiction zone" – and the "outer zone" beyond it were under the command of Toronto police.

Even after a column of black-clad anarchists broke away from a larger labour march on the Saturday of that weekend to smash shop windows and torch police cars, Toronto officers remained at the security fence a few blocks away. In the report, Chief Blair suggested officers were afraid the vandalism was a tactic designed to draw police away from the summit site.

"The Toronto Police Services' preoccupation with protecting the [fence] detracted from its ability to police the rest of the city and caused a policing vacuum," Mr. Morden wrote.

When Toronto officers began the mass arrests on Saturday evening, which netted mostly peaceful protesters, another problem emerged. The temporary detention centre had only one court services officer to prepare the detainees to be booked, given access to a lawyer and have handcuffs removed. The bottleneck meant some people were held 24 hours without being processed.

Story continues below advertisement

The report is the latest on the policing operation and contains the strongest language yet on the role of the federal government.

"Did [Chief Blair] make mistakes? Yes. Are they being dealt with? They should be and they will be. But to blame him for everything is to pretend that the federal government had no role in this," said Councillor Adam Vaughan, a police board member at the time.

Nathalie Des Rosiers, general counsel to the Canadian Civil Liberties Association, said if the board had been more rigorous, it may have detected flaws in police planning. On one occasion, she said, Chief Blair was asked how policing across the city would be affected by the force's commitment to the summit. He replied that there would be no problem, and no one pressed him further.

"The fence became a symbol of what security meant for the operations," Ms. Des Rosiers said. "If no one touched the fence, it was considered a success, as opposed to recognizing that the security operations had to encompass both the rights of protesters and the rights of businesses."

With a report from Elizabeth Church